I would get something handbuilt from a reputable wheelbuilder and stay away from machine/pre-built wheels, you will be much happier in the long run.jnstrom said:
Depending on your budget, you could get something decent for a few hundred. Most midrange hubs will be fine, but the rims I would recommend for a clyde would be: Sun Rhynolite (cheap, but heavy at 565g), Mavic XM719, DT Swiss Ex5.1, Velocity Aeroheat. The last 3 are great high quality rims, around 440-500grams and are a bit more pricey. All of these rims build nice, light, and strong wheels for an aggressive XC riding clyde.
Good luck!