You can get a Z4 2.1 speaker setup, so if you lie them, you can add a sub. But you sold them. I use Audioengine speakers for my computer and I'm very happy with them. Very good sound and good bass. Lastly, you can't buy a surround speaker setup worth a darn for your budget.
So I had logitech Z4 speakers and they were great. I used them for normal music listening to and I also hooked them up to my HDTV so when I watch movies, it sounds great.