By far the best quality speakers I've seen in a long time is Creative's Inspire 7.1 Series. I use the Inspire 7.1 T7700 back in Chicago, and have been using them for the past 2.5 years. I seriously can't complain about anything except for the sub, which is some 48W peak 6.5" sub. I hotwired the sub output to the input on two 12" Powered subwoofers to take care of that problem quite nicely. The two subs were 200W Peak (100W RMS) for $80 each, and definitely do a good enough job of making up for the lack of bass in that system. The whole thing is pretty cheap.
Otherwise, I just upgraded someone's system for them with a Logitech Z-5300e system (280W 5.1 Surround).
http://www.newegg.com/Product/Product.asp?Item=N82E16836121121It sounds really nice on the X-Fi Platinum sound card too. The bass could be a bit deeper, but its pretty nice overall, and the mids are exceptional. For $135, I seriously couldn't complain.
Then again, I'm not sure how well some of these PC multimedia speakers will run off of a 2-channel input in 5.1 or 7.1 surround mode. All I can tell you with 100% certainty is that your speakers will only sound as good as your sound card. A good sound card is crucial, and this is coming from a guy who bought an X-Fi Platinum over an Audigy 2 NX and saw a HUGE difference. My onboard 5.1 surround is serious shit compared to my X-Fi. Just a bit of a suggestion if you can afford a good sound card.
I have an Audigy 2 ZS for sale if anyone wants it too btw. Just name your price.