RF 501BD, they are on sale at ultimate electronics for $400, so i bet they are fairly cheap online.
the 500/1 from JL should be sufficient also, but a new amp that caught my attention is the diamond audio d3 series amps. they have a 600 watt monoblock (i believe its 2 ohm stable) for $319 RETAIL. my diamond audio statements are a little bias //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif but i feel that they have great products, $300 for a 600watt monoblock from them is quite nice.