I currently own a Sapphire 5850, after reading the front page article, i'm stuck between whether to get another 5850, or selling my current one, and getting a pair of GTX 460s as my future upgrade path.
My motherboard is an ASUS P6T Deluxe V2, so both setups would be fine.
Hocp also just did a GTX 460 sli article against AMD gpu's. They chose only to do 2560Xxxx tests. 5850crossfire does not destroy 460sli. http://www.hardocp.com/article/2010/07/26/geforce_gtx_4... I would not return a video card to do what the OP has proposed. Restocking and shipping fees for returning a working card because of change of heart ?
5850s are selling for ~$200 used now, so its a a great idea to sell it.
However, buying a used one for $200 is probably your best choice, as you're getting better performance for the same cash as a GTX460 SLI setup.