There is a new one in my neighborhood, called "The Corner Vet" that I plan to take my old hound dog to next week. The rates just look fantastic and you don't need an appointment.
There is a location in Plano, and other places, as well.
I usually will go to the SPCA to have pets neutered, etc., but sometimes, you just need a local vet, and mine is super expensive (most are).
This one looks clean and nice, from the outside, and the rates sound good. Haven't experienced it, yet, but thought that it would be another option for you.
Good luck!
http://thecornervet.com/richardson