If $250 is too steep don't do it. The reason you had a problem was a machine built wheel that was probably never re-trued from day one. Go ahead and get a regular 135mm mtn. wheel and put an 8spd cassette on it, assuming the rear triangle is 130mm and not 126mm.
http://www.bikeman.com/WE7095.html $125 plus shipping.
If I was building for a 300lb person I'd be inclined to go to 13g butted spokes and wider rim like the rhyno for 40mm tires.