any wheel you buy is likely going to be a BETTER wheel than the one on that bike. I'd suggest the handspun wheels 'pavement series 5' (or 5.1), these use deore hubs (suitable for 7-10 speed cassettes) and mavic or velcity dyad rims, about $100 each (front, rear). handspun is distributed through QBP, so virtually any LBS can order them, or you can get them online. they are made with DT stainless spokes, and are quite well made. you can't buy the parts for what these wheels cost.

there /are/ some $50 wheels, but they are pretty junky.