OK well heres my suggestions since you already have a hu here is a decent 4ch amp, If you ress make offer, offer 100 and it accepts it //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif, Thats how i got mine.
http://cgi.ebay.com/CADENCE-TXA-3004-STEREO-AMPLIFIER-BRAND-NEW_W0QQitemZ310087234032QQcmdZViewItemQQptZCar_Amplifiers?hash=item4832a3b1f0&_trksid=p3286.c0.m14. This has free shipping.
These componets are 35 a set+ shipping so should be like 45 shipped
http://www.millionbuy.com/pows6c.html
Then that leaves you 100 to play with to get cheap sub, amp and box. I would say if you added about 100 more for a total of 350 it could be a decent budget system