I just build a 2.1 system with a pair of Infinity Primus 150s, Bic H-100 sub, and Onkyo TX-SR504 receiver. Once my receiver gets back from the repair shop I'll hook it up to my computer via SPDIF from my Audigy 2. The speakers, sub, receiver, and adapters/wiring came in around the bottom-to-mid $400s. If you're willing to spend upwards of $500 for 2.1, you might as well skip the "computer only" speaker sets and get something you can upgrade as you see fit. That was my train of thought a few weeks ago when I was in your shoes, anyway.