The Monsoon speakers mentioned above and the ProMedia 2.1 (also mentioned previously) will tend to offer better all around sound... that is a fairly good balance of highs, mids, and lows. The Altec Lansings mentioned above will tend to sound fairly nice but a little more muddy than the ProMedia speaker system. The Z-560s will offer very apparent bass with decent (along the lines of the Altec Lansings) highs.
So based on what you're really looking for, I'd get either the ProMedia 2.1, Z-560, or MH505.
EDIT: Refurb ProMedia 4.1 ... I wouldn't buy speakers refurb. Even if Klipsch was the ones that fixed them to factory specs.