I've got the logitech z5500's, which are basically their top of the line 5.1 speakers. I like them, and for games and movies they're great. People rave about the sound of them, and they're meant to be the best computer/entertainment this money can buy, but in all honesty they're not great. The mid is pretty rough - classical music sounds poor though them - but the bass is strong (as you'd expect with a 10¨ sub). It just feels like there's too much to a gap between it and the satalites. If you're listening to audio through a 5.1 setup it's not how it was intended to be heard, but you can switch (certainly with the z5500) to stereo if you want.
On the plus side they're very listenable, it has a lovely controller with loads of inputs, the speaker cable is generous and it all looks great.
But when I compare them to my PMC 2 way speakers it's night and day. The PMC's have so much detail, a great 'easy' sound (the z5500 sounds a bit like it's trying too hard). I'd recommend getting a pair if you can find them. Here's some in the uk which won't be much use to you, but if these double in price it'll be $300. Then get yourself a nice little integrated amp and you're set.
http://cgi.ebay.co.uk/PMC-TB1-Monito...QQcmdZViewItem
It will sound so good, if you haven't heard good speakers before it's an ear opener...
Whatever you do don't buy a cheap pair of bookshelf speakers off bestbuy (or whatever those sites are called), they'll be awful. I spent the weekend listening to a pair of Linn bookshelf speakers my dad got cheap - they're so bad. £2000 they cost ($4000) and they're rubbish, so money don't buy you quality. I can vouch for the pmc's, try to find some
my 2 cents!