I would look at the numbers on quality amps - Lexicon, Krell, Bryston, etc., and try to get as close to those as you can. For S/N, you want the number higher, for distortion numbers, you want them lower. On pro amps, they worry more about 2 ohm suitability, bridging, crossovers, and power than the audiophile sector. But you can find all the information need to make a good decision. The QSC website has some good information on amp design and power, and their forum is run by real techs - just don't expect a HT tech.