970s are around $300 as well I believe... Anyway, I would go with the 970 simply because it is a newer card with comparable performance. It also has double the VRAM which is becoming more and more important in newer games. 2 or 3 way SLI is also a much more reasonable possibility with the 970 in the future. Driver support will be better, games will be better optimized, cooler will probably be a little better.
The reasons for the 970 are stacked, the 690 was good in its time, but no reason to go backwards in your situation.