My advice: Hunt.
My current computer setup was purchased over the past two months. I picked up a pair of PSB 400i speakers on E-Bay for $60 (had to do some equalization: they are rather colored, but very pleasant / room filling) and an Energy 8" sub for another $60 (for more space-filling, there's a 12" infinity at my local pawn shop around the same price).
So $120 and I have a pair set that I think will sound better than Sony's low-end will.
I also picked up a pair of Kef Q-series I might be willing to resell, I find them too bright.