Our favorite amps are Carvin DCM4000's:
http://www.carvin.com/products/dcm.php? ... 00&CID=PWA
They are not for the faint of heart, but you can't beat them for large venues. In essence, it's 4 seperate 1000 watt amps (@ 2 ohms), or up to 425 X 4 continuous at 8 ohms. It runs about a thousand bucks, but has 2 seperate plugs and is bridge-able. We like the redundancy. Not lightweight, but we have them rack-mounted into custom boxes. And if you don't need all that power, just run two channels not bridged.
Sometimes we'll use one of them to run 2 EV Eliminators, 2 EV Eliminator 15" Sub enclosures, and up to four other fairly large speakers, and it doesn't even flinch. If you can't tell, the Eliminators are our favorite speakers, too. The sound is amazing, but they are big- we cart them around by trailer and handtruck them in.
These sound really good:
but add one or two of these, and the sound is incredible.
http://www.musiciansbuy.com/EV_ELIMINAT ... MISUB.html
For portable applications, we stack the mains on top of the subs with poles, and daisy chain them together. They have built in Crossovers, and parallel ins/outs.
"If you can't hear it.... you'll never understand it." -Satchmo