Small breeds suitable to live with large breeds

 I also think it makes a difference whether you adopt a puppy or an adult.  If your Corgi was an adult when you got her, I'm not surprised at the reaction.  In any case, most dogs accept puppies more readily than they accept adults unless they have an extensive socialization history and are a breed that generally likes other dogs.  With Dobes, I would pick a female if there's a male in the home, but I would not hesitate to choose a Lab female either.  I would stay away from the DA breeds and choose a dog that is not pushier than your resident dog.

 Was Bixby an adult when you got her?

Casey LOVES big doggies :)

If you're going with something smaller - I would go with a terrier of some sort, since you don't want a corgi

 GSDs are also very prone to same sex aggression with dogs they live with. Bringing in a male Dobe with a male GSD is just asking for problems. I thought you were looking at Collies, another GSD or a Bull Terrier?

  As for the same dog and large dog thing, a medium small dog should be ok. The Corgi was a good suggestion a couple others would be a Beagle or a mini Bull Terrier. Smaller but study dogs with some substance. Our GSD and Corgi play great together. I would not suggest getting anything smaller than a Corgi as a playmate for your GSD though. There is too much of a risk of predatory drift or the smaller dog getting accidentally injured in play (one wrong move can mean a broken bone). 

My intact male GSD gets along fabulously with my neutered mutt, however the mutt is more submissive, very laid back dog (neutered very young in rescue, never once has lifted his leg and is always mistaken to be female).  He kinda lets Nikon think he runs the show.  No same sex aggression but their temperaments couldn't be more different, and they are a good match in size/play style.

I would think several types of terriers might be sturdy enough and energetic enough to keep up with a GSD.  My SchH trainer has a Cairn b/c he wanted a hardy little dog for his kids and it sounds as though the Cairn runs the show.

I think the prey thing is really going to depend on your dog and how much prey drive HE has.  Nikon has a lot and cannot be around cats or toy sized dogs.  There's no amount of training or forced socialization that can erase genetic drive.  On the other hand, my Kenya has never shown interest in my cats and they were comfortable with her around within a few days.

Jason who posts here sometimes has a Corgi, a crazy drive working line GSD, and I believe a GSD mix.

 I would probably steer away from a bull terrier if Tbone is at all confrontational with other dogs.  The ones I've known were not for the faint hearted, very domineering with other dogs, and prone to OCD behaviors.

 If you are considering a JRT the JRTCA website is a must visit! It is probably one of the best breed club sites out there with tons of JRT info, info on living with JRTs and even a quiz to help determine if you are a suitable JRT owner: http://www.therealjackrussell.com/index.php

Good advice to check out the JRTCA site.  I would add that before you consider a JRT, spend time with the breed, in person!  These are not the breed for the laid back dog owner or for anyone who doesn't have a real grasp of just how "terrier" they are.  They are a very affectionate, happy, energetic breed but they require an experienced dog person with time to properly socialize and train them to be good citizens. 

 So affectionate, it HURTS! LOL  And they're a lot bigger than you think they are. Emma could pull harder, go farther, last longer than most of the big dogs I've known, and if they got in her way, she just ran over them. Determined doesn't even BEGIN!

 Lexi and Freya are 3 months apart. We watched them like a hawk to make sure Freya was playing nicely. We've never had a problem and they play all the time. They play tug a war and sometimes... Freya lets Lexi win.

 Lucy was the one I was worried about when I brought home Lexi, she was old and her and Sammie had some issues in the past. But they turned into the best of friends. In fact, I think Lexi was the only other dog Lucy liked. Sammie also had no problem with Lexi coming into the house hold.

Beejou

 

Thanks for the input, everyone. T-Bone is the least confrontational dog I've ever met. He;ll take any amount of crap off of any other dog, but part of this might be that he's still young. (My good friend has a GSD just one month older, however, and he certainly doesn't put up with nonsense from other dogs) I have only met a very few Bull Terriers/Mini Bulls, so a lot of research and meeting the individual dog would be in order. I was raised with Jack Russell Terriers growing up, my grandparents bred them, and I'm used to how fiery they are, LoL. It would probably be a good idea to pick a female dog regardless of breed or size, you guys think? Not that T-Bone has any issues with males but I want them to have the best conditions for a great relationship.

 Yes I'd say your best bet would be getting a female. Even though your grandparents had JRTs, you may still want to check out JRTCA's website. The parent club for Mini Bulls also has a website with info which might be a good place to start research: http://www.minibull.org/

This site also has good info on common problems with Mini Bulls, such as OCD behaviors: http://www.envisionregistan.com/healthrescue.cfm

My basenj, Chaos, weighs 22 pounds.  That being said she holds her own with my Catahoula, Keisha, that wieghs 56 pounds and my boyfriends dog that weighs 87 pounds.  She has also been known to have playdates with my neighbors german shepard and the dog down the road that is a chow mix.  These play dates were set up as my bigger dog runs out of energy way before Chaos is done playing.  I also have to note that if anyone yelps, its ussually the bigger dogs.

I sure like the looks of a Besenji, but I like "velcro" dogs, lol. I've heard Basenjis are independent and not super affectionate - is that true?

Beejou

I sure like the looks of a Besenji, but I like "velcro" dogs, lol. I've heard Basenjis are independent and not super affectionate - is that true?

 I have quite a bit of hands on Basenji experience. I can say that while there are people who just LOVE them, many pet owners would find them to be really difficult and "strange". Not generally "velcro" dogs, sort of the opposite of GSDs really :) They are a very primitive type of dog and their behavior reflects that. They tend to be very independent, great problem solvers (think: escape artists!) and very predatory towards small animals. And that whole "Barkless Dog" thing? They don't exactly bark but that doesn't mean they are quite and there is nothing quite like a Basenji scream (which they do out of excitement or frustration). There were a couple at the grooming shop that were screaming because they didn't want to be in a cage. It was so loud and sounded so bad that the next door neighbors came in to check to see if anyone was hurt or needed help! This is a good Basenji resource: http://www.basenjifiles.info/BasenjiFilesBasGuides.html