You should also do yourself a favor and check out Hsu Research (www.hsuresearch.com). They offer a subs at many price points, some with built in amps, others with seperate amps. All are available only from Hsu on a 30 day trial.

I have a velodyne f1200r in my 2 channel system and a Hsu tn1225 w/ 500 watt amp (about $1k) in my HT setup. The Hsu was easy to set up and sounds fantastic.