Elemental Designs NINe.1 for 350 its less if ur a forum member. ill get tha link later on. Consider Crossfire VR-1000D for 420 shipped at woofersetc.com, dont know how long its going to be on sale for though.
Get a hifonics bxi1206d and call it a day. One can be had on ebay for about $210, but im sure if you shop around a little bit you could find one cheaper. It should do around 1000 watts b/c hifonics is just a bit overrated.