An entire Schwinn World is worth about $100, so I'm not sure that it makes sense to buy wheels for one. I'd go the other way and sell the bits I have for whatever I could get.

There are so many options out there, and they all come down to what tool is best for you. You can get a lot of used bike for $500 on Craigslist - like a very high end 80s-90s tourer. Those make great commuters.