With that budget, I'd probably look at something custom-built from a reliable wheel-builder in your area. That way you could get something that totally suits your style of riding, along with any other specifics (weight, durability, spoke count, rim depth, hubs, bearings, etc.)...that you wouldn't be able to spec out on a factory wheelset. Do you climb a lot of hills? If so, then you might want to look at a wheelset designed for climbing. If you ride a lot of flats, then perhaps something a bit more "aero" might suit you better. Or, just stick with a general "all around" training wheelset.
I too, am looking at upgrading my stock wheels. My budget is quite a bit less than yours, though. At the moment, I'm looking at 2 different wheelsets - the Williams System 30's, and the Shimano RS-80's...both are billed as an "all around" training wheel and have good durability, which are the 2 characteristics that I'm looking for. Plus, they both fall into my price range of $5-700.