I have used a number of pro PA amps, and to me, it is hard to beat QSC's PLX line. Their combination of power, clean sound, reliability, and light weight is excellent, especially considering the price point. Crown makes a number of great amps as well. I use a PLX 3002 in my bass rig (3,000 watts into 4 ohm, bridged mono!), and it allows me to have gobs of headroom without breaking my back!
Tom.
Tom.