You can always sell it
, There are people who will snatch it on instant.
And to answer your question - NO- it's not worth it
Almost any 5850 is getting to near 900/1300. The best part is the memory - ITS ABSOLUTELY SAME as on 5870. Its just there is no any different chips at the moment so all chips used are same on all 5000 series
my 5850 (Sapphire stock) clocks to 880/1260 without any issue and I havent pushed it further
as my power supply is turning off
(as its 400W) I will upgrade it soon and will check its full potential