Just a bit of an update guys.
I have bought the Z5500's, and although the jukebox isn't ready yet, I have had the speakers connected to the PC it's going to be used with, and well.... I am so pleased with the sound quality and volume. I didn't expect it to be so loud and crystal clear as it is. I am pretty hard to impress when it comes to sound as I used to enter my car in the sound off competitions in Adelaide South Australia, and I actually got 3rd place one of the times. Now.. we're talking this was an $18,000 sound system so you can't compare it to the logitech speakers.
I guess what I'm saying is that I think it'll do a great job for some serious parties, and as for the bass... it's not too bad at all, plenty of thump.
2 thumbs up for the logitech Z5500's.