this is a tough one actually.
reason i say that is because, you can now get a new X1950 pro for around £100 and they outperform the x1800GTO. So the question is, would anyone be willing to buy a 2nd hand X1800GTO for a higher price than a new x1950 pro?
what you might wanna do, is put it on as a bidding item rather than buy it now and just set up a reserve around £100 to see how much people are willing to pay for it, if not more than your reserve. That would give you some idea.
I can see on ebay now that the X1800XT is selling for around £90-100. so i would be quite suprised if you did manage to sell the x1800GTO for 120. Then again..i managed to sell my 7800 GS for 150 to buy the x1950 pro :roll: ...so technically it was a free replacement.