I picked up a set of M-Audio AV40 Studiophile speakers a few years ago and I've been pretty happy with them so far. I was using 5.1 prior to that, but I found them a bit of a burden. If your computer desk is in the right position and your room is built a particular way then they can be excellent, but the extra cables and hassle they bring sometimes aren't worth the added immersion. Finding a decent set of 2.0 speakers completely changed the way I listened to music, watched movies and played games, just like when I moved from 2.0 to 5.1 or 7.1 changed my perspective in the opposite direction.
Personally speaking, I think 2.0 is better for music, unless you only listen to Hip-Hop, Trance, Dubstep, House or other styles that generate a lot of bass. I have found that a reasonably priced audiophile 2.0 setup, albeit weird at first, offers finer clarity than a reasonably priced and solid 5.1 setup. That extra thump and bass often masks the details of genres like Rock, Blues, Folk, Indie, Traditional, Classical, etc., but as I said, they can be essential if you like to feel a thump. If I'm listening to Doom Metal and I want that 'thump', I just turn them up really loud and then I'm happy. They push more air and I can feel it without ever sacrificing clarity or nuance.
As I said, I'm happy with the AV40's and they've inspired me to stick to two speakers rather than 5.1 or 7.1. My next speaker purchase will probably be a £300 2.1 setup—I do like that extra bass sometimes. However, if my room was smaller, I had less people in the house, the cables were easily managed, the speakers could be elevated or attached to the ceiling, and I was willing to invest more money in high quality tweeters, then I would consider going back to 5.1. But as it stands, although you lose some immersion, you gain clarity, warmth, and a more in-your-face pronunciation.
With all that said, that's just my experience, and I recognize that others have different views. So if you really love 5.1, and I totally get why, then I suggest finding a set that is specified to have greater clarity than your average Logitech gaming set. Go to an audiophile forum (I've used head-fi.org) and ask about 5.1 speakers that are a little more sophisticated than your average 'thump thump thump' surround sound speakers that, in my opinion, offer more fake immersion than real quantifiable depth. I'm not completely against 5.1. In fact, I may go back to it when I move, but currently I'm happy with 2.0 and the M-Audio AV40's I have are good.
I've heard good things about the Corsair SP2500 and are on my personal shortlist, but they are out of your price range. The SP2200 are cheaper but I don't think they're made any more.