Wheel set for a single speed

I recently bought a pair of used bikes, a Giant Bowery with Alexrims DA22 and a Specialize Langster with Alexrims S480 on them. I want to use them for training. I ride a Specialize Roubaix but have really enjoyed riding the single speeds (freewheel). The DA22 seem adequate, however the S480s seem cheap. I'm looking for suggestions on what would be a good wheel set with out spending more than I paid for the bike. I think I can keep the DA22's. It's been suggested that I look at getting a set of Vuelta Zerolite Track wheels from Nashbar for around $150. I ride with a group a couple days a week and can stay with them on the single speeds, it's just the Langster feels sluggish. I'm not even certain where these wheels fall in the cost chain. Any suggesting a would be appreciated.