Creative Systems are very good. But personally, I prefer Logitech systems, I think they have better Bass and are better to my ears.But that's all personal.
Go for the one u like, it's not easy to hear the differences between them.
If u r big on games, i suggest u get the lowest end X-Fi chip, EAX effects are way better than software sound and really give me the edge, especially in FPS games (BF2142, CS:S) cuz i can hear exactly where the shots are coming from. I don't know if ur card has EAX feature but if it does, then there is no reason to upgrade.
Get 5.1 speakers, u will appreciate it cuz u will enjoy music, games, and movies much better this way. IMO 7.1 are a waste of money
- Hope this helps.