Amazon.com has the Logitech Z560 Speakers THX Certified, 4.1 Surround Sound, 400 Watts for $101.34 after a mail-in rebate. I have these speakers and they sound incredible. They very similar and comparable to the high-end Klipsch ProMedia 4.1 THX Certified Speaker System, but at less than half the price. Several CDRLabs members have the Logitech Z560's and have said nothing but good things about them.
$141.34 - $40 Mail-In Rebate = $101.34 HOT!
Logitech Z560 Speakers
Rebate can be found Here