Personally the 2.1 will work fine in you situation. Unless you can properly place a 5.1 sound package, you are not going to benefit much. Besides that, not everything on the computer will be in 5.1 anyway. Most stuff will still only play in 2.1 or prologic mode (depending on settings) unless you are playing a game or software that actually supports 5.1, movie playback, etc.
I actually do use a Digital receiver for my setup, but I had the room for it. To buy the system I run including the speakers is probably near a grand. (when I bought it). Anyways. Just get a nice 2.1, you won't be disappointed, especially if you get a decent set. I have a couple of decent logitech packages setup for family members and they sound perfect!