I had a set of Klipsch "computer" speakers which were ideal for their portability, I used them at a lot of parties. Plenty of volume and the sytem wasn't so big it was a hassle to move it. Unfortunately they got cooked in the fire and I really haven't gotten around to replacing them. The sub was 33 pounds so it wasn't something wimpy, it had 5 satellites. There was a few types of inputs on the back including standard mini jack, you could plug any audio source into it, ipod, radio etc. I think I paid $450 for them but they had issues and apparently were never really up to Klipsch standards or I would buy another set if I could find them.
What I'm looking for is something similar with 5.1 capabilities but what would be ideal is something that could be switched to stereo so it outputs audio over all 5 satellites.