The simplest way to find powered speakers, is to look for PC ones - and if you want some meaty bass, get a set of 2.1 (Subwoofer/control unit with small satellite L/R)
Looking over ebuyer, there are a TON of them
http://www.ebuyer.com/customer/produ...duct_uid=65704
Check the reviews, not perfect, but generally good - and a 2.1 set for the price of most pairs - of course. you can get a powered pair for even less, or move up the range if you want.
To a degree, it does depend what you're used to - I've tried several sets on my PC, and my originals, bought to go with a very expensive SB16 and 2x CD-ROM, have stayed with me through 3 systems - finally moved on to a 5.1 set.
NB. A 2.1 set is normally single jack operated, the subwoofer/control does the splitting.
A 5.1 set is 3 jack, all channels seperate, but many also have an additional input for plain stereo - but anything more than 2.1 is pointless for a stereo source.