There's loads of brands... Every brandname that has been around, and has those thingies around 2500$ is about worth it I guess.
Crest, Crown, QSC,.... All big brands and pretty big prices.
What speakers do you have? That's a major part of the decision.
I just got into the whole ampspeaker stuff, so I don't know the whole lot of it. With my live-mixing experience, I can tell if a system sounds good, but what is wrong with it, or which systems to buy is something different. (I just bought a new system for our youthclub, and got a job as a stagehand with a local soundcompany...)
Ow, and I forgot to mention:
HIP BIP!!!!
HIP BIP!!!!