I really wouldn't recommend the DTT2200 unless you have a SoundBlaster Live! 5.1 card (the kind with built-in Dolby 5.1 decoding). Even then, I wouldn't recommend them unless you wanted to save some money. The DTT2500 and DTT3500 models have their own Dolby 5.1 decoding, which will take that burden off your computer.
As far as quality of sound goes... the DTT2200, DTT2500, and DTT3500 all have about the same quality sound. They're the same thing, really, with different features built in. The DTT3500 is the nicest one, as it comes with a remote control.
The CSW FPS2000 is only a 4.1 system, I should note. There's no center front speaker like in the other three CSW models you have listed.
Some people don't care for the quality of the CSW speakers, but I happen to like them because they have an advantage that other speakers don't - they can utilize a direct digital connection from the SB Live series of sound cards. If you don't have an SB Live, though, this will probably be useless to you.
Labtec and Altec Lansing are quite definitely inferior in quality, but depending on how much of an audiophile you are, they may be worth it for their lower price. Altec Lansing speakers certainly aren't bad, especially for the cost. I would probably stay way from Labtec, though.
I've heard good things about the Boston Acoustics. Those who have them swear by them. Unfortunately, I've never had any experience with them. I'm a Creative Labs / Cambridge Soundworks fan, myself. I happen to have the DTT2500 set and am quite happy with it (though I do sometimes wish I had the nifty remote control on that DTT3500!).