$1000? Not a chance. You could build a system that would crush that for less than a $1000 and it's used and old and outdated. Used PC's are like used cars. You never get in what you put out, and the owner always values it way too high.
And just because a old GPU is rare, doesn't mean it's worth anything except maybe to one person who wants to SLI it.
So what would you suggest I do?