Do NOT use AAMCO. For a very brief period of time I took my fleet trucks to them. After a lot of trouble and a "nice" letter from my lawyer, on my last work truck they ended up installing a GM reman'd unit straight from a dealership. On their dime. Since then I only use GM reman'd units and install them myself. The write-off isn't worth that much headache.
It's extremely difficult to find a reputable trans shop now a days.
As for my personal vehicles, I rebuilt them myself for a number a years with good success.
Some track buddies of mine had great luck with Finish Line Transmissions out of Illinois. Their level 3 is a great reliable street unit for the budget minded. The problem is, if you're not doing the labor yourself it could get expensive with the shipping and paying a shop to do the labor.