it all comes down to what you want out of your new audio system. here are a few questions you might want to ask yourself:
----
do i play FPS and MMO games more than RTS and other games? surround sound can let you know if something is behind you - can you do without this?
do i watch alot of movies on my pc? do i want surround sound or is stereo fine?
do i listen to alot of music on my pc? would i prefer better sounding speakers instead of a cheaper 5.1 system?
how much am i willing to spend? in total, or right now? (upgrades in future?)
would i be interested in getting a cheap a/v receiver, seperate speakers, and seperate sub.. that i could pair with multiple devices? (and upgrade later)
----
if you decided on a good 2.1 system,
i'd recommend the klipsch promedia 2.1. a little pricey, but excellent speakers for the money. (i had a set). the only downfall is that the sub overpowers the satalites a tad so you will need to adjust the equalizer or lower the sub volume.
if you decided on a $400 or less 5.1 system,
i'd recommend the logitech z-5500. (as you were thinking) it might not be new tech but for the money it is still a very nice system. the system has faults but for the money it is hard to touch another 5.1 with similar features.
if you decided on an a/v receiver 2.1/3.1 system with the potential to upgrade,
the great thing about using a few bookshelf speakers and center channel is that many local electronics stores (hhgregg, best buy, etc..) will have theatre rooms set up for you to test out the equipment before you buy. in the long run you might spend a bit more on equipment but the sound quality is much much better. if you plan on using the speakers for more than just your pc this is definitely the way to go. you can plug in your pc, dvd player, console, and more without needing to buy seperate speaker sets.
afterthought:
best buy also has a few computer speakers on display that you can test out in store. i know they have the klipsch 2.1 and logitech's on display.