No gaming?HIS 5750
is a good buy in the states. You could get by with less, but it's in the same price bracket of 6670s, 6570s, and 5670s that it's faster than.
If you're looking for general advice, pick up a card with GDDR5 memory if you can, just in case you decide to do light gaming. GDDR5 is about twice the speed of GDDR3. 1GB total VRAM is plenty.