Just did a comparison between the Alesis/Logitech 5.1 System and Klipsch ProMedia 5.1. Very interesting! Based on the specs, the Alesis/Logitech appears to be the better speakers. The A/L system has a System frequency response of 35Hz-20kHz, where as the K system has a frequency response of 25Hz-20kHz. BUT... suprisingly the A/L has FOUR source inputs: digital optical, digital coaxial, 6-channel direct (3 stereo-mini), and analog stereo-mini. The K has only ONE, 6-channel three stereo-mini plugs).
If you would like to read a guide to studio monitors this one is a good starter. It maybe more money than you are wanting to spend. However, when you buy something cheaper it's good to know where the deficiencies are.
The M-Audio Revolution 7.1 card with 6 of the M-Audio SP5B nearfield monitors would only cost about $700 from MusiciansFriend.com. Of course that doesn't include a sub for the LFE, but if you are just doing music at the moment, the sub could be a wish list item and you would end up with a decent pro quality system.