Bartons options were better.
Keep that card for a while, you have no reasont o get a DX10 card yet
Wait until some native DX10 games come out and see how the first gen DX10 cards perform.
If they are a success then invest in one.
Or if you really can't wait, get one now
But don't expect to get alot for your card compared to retail price.
EDIT: I strongly advise against the 320mb version. Most cards with 256mb of RAM have already shown to struggle in DX9 games, 320mb could end up a dead end for DX10. I could be wrong, but that is why i advise waiting this one out.