5.1 provides the surround you more type effect with that type of separation over simply hearing stereo with a bass boost with a 2 1/2 set. Logitech is one of the top for the low to mid price range and the most popular due to the sound quality their speaker sets offer.
I grabbed a set of 5.1 Z-640s and wouldn't part with them fior $60 at a pc show. Youi can look over some good sets by Logitech at
http://www.newegg.com/Product/Produc...08151&name=5.1
There the X-530s are seen for only $54.99 OEM at
http://www.newegg.com/Product/Produc...82E16836121126 70watts rms like seen on the X640s used here is adequate.