I don't know about either as I could only justify getting a 9800gt mainly because I wanted Octane as well
so I got both instead of a GTX.
My theory is if you can afford it get it.
My setup is not that old, and I'm finding running all the recently updated software packages
is stressing my system, hence the new but older graphic card.
Future proof, maybe not, but delaying the inevitable while saving for the next best thing is the way to go IMHO
Luke