looking for a particular breed...

My mom had Anatolians - they lived with the sheep flock and kept the coyotes away - she was happy with them.

If you want a true guardian, you need to go to kennels or folks who actually produce life stock guardians.  You also need to decide is this dog going to be a working dog or a pet.  It can be hard to combine the two when you want a dog to deal with coyotes and stray dogs.  Those I have come in contact with in herding, are put away while new dogs and folk are on the property.  They are fine with the dogs and people that belong to the place.   These dogs a decidedly independent (they have to be since they work alone most of the time)  Keep that attitude in mind when considering the specific animal you want.  There are some nice websites with links etc if you do a search.

Farmers around here use Great Pyrenees to guard their sheep. (That, or llamas LOL)

Maremma Sheepdogs are a good balance between alert protectors of the farm and "people friendliness".  Anatolians (Karabash), Kuvasz, and Akbash dogs can be a little more aggressive to people and unwilling to accept strangers.  They can also be aggressive to your other farm dogs.  This goes for most other guardian breeds such as working Komodorak, Kangal, etc - the more primitive, the harder they are to train to your specific needs - you are working with raw instinct. 

I train my livestock guardians to accept people, from an early age.  While bonding, guarding and patrolling behaviors are instinctual, you must train behaviors such as setting boundaries, respecting fences, accepting certain types of intrusions, and you also must extinguish undesirable behaviors such as playing with young stock, fence breaking, and resource guarding (keeping stock from food set out).

Pyrs are terrific too though more high maintainence - and it's easier to accidentally get a mostly show- or pet-bred pup that will have little to no guarding instincts.

Please feel free to PM me if you have any other questions - I've got several years' experience training livestock guardian dogs for farms all over the country.