How bout these
http://www.ebay.com/itm/Shimano-Ulte...item4cfb46315b
I rode dura ace hubs on 32 spoke open pros at 275 (now 245 going to 220) and they stayed true.
If you think 32 would suffice
http://www.ebay.com/itm/Shimano-105-...item3a6b0c7e96
More expensive
http://www.ebay.com/itm/Velocity-A23...item35a4b8b243
But I'd prefer the Ultegra hubs
But then again (from another post), the owner of this bike is 392 down from 424 and says those wheels are doing fine!!!
I would be worried about these at 250!!