You've just learned a valuable lesson...
I hate to say it, but starting over may be your only alternative. The receiver you purchased in the HTIB (Home Theater in a Box) is rated at 10% THD. It isn't just your speakers, although you're right to want to replace them. Your rcvr is delivering quite a bit of noise to them. At this point, purchasing new speakers will only exasterbate your problem, leaving you with even less money to solve it. If I were you, I'd deal with it until you can put together more money to get a new system entirely.
Some budget solutions...
Good ($1,150) - Yam RXV457 Rcvr, Yam DVDS550 DVD Player, Polk Rti4 (F/R), Polk CSi3 Center, Polk PSW10 Sub
Better ($2,070) - Yam RXV657 Rcvr, Yam DVDS550 DVD Player, Polk Rti6 (F/R), Polk CSi5 Center, Polk PSW303 Sub
Much Better ($2,300) - Yam RXV1500 Rcvr, Yam DVDS1500 DVD Player, Focal-JMLabs Sib Speakers
Also, you might take a look at the classifieds here and at audiogon.com to see if you pick up some used equipment and lower your cost. Either way, in Audio/Video, you get what you pay for and a $200 HTIB is going to sound like a $200 HTIB...
**CC return policy is 30 days, just like us...