This isn't terrible yet, actually. A perfectly good low-mid-end gaming build if an equivalent one were made today. I see that isn't what you're going for, though.
Here we go.
-One new 120mm fan, $10. Stick it on bottom; it's pretty cool that the 690 can do that. http://www.newegg.com/Product/Product.aspx?Item=N82E168...
-One more 2gb RAM stick, if you can find a matching one. If not, a whole new 8gb set.
-TWO EVGA 012-P3-1570-AR gtx 570, $680 ($340 each). External exhaust is good for SLI.
That's $1050 plus RAM, and you've got a wicked build. This is essentially a $1600-$1700 build with scavenged parts.
Alternately, you could go 560 Ti SLI and get a Crucial M4 128gb or an ADATA S510 120gb SSD.
You don't need a new PSU. Components don't use more power as the years go by. Recently they've held pretty steady or slightly decreased at the high end. That one should work fine for a few years more.
You could wait for the next GPU series forever, but that won't get you anywhere. The 7970's beastly, but it's not a good value. You'd need to be spending more, I think. Plus, it sounds like a jumbo jet.
Don't blow it up, kids have two systems side by side upstairs and there's really not a huge difference in observable game performance .... yeah the 560's get 40 % more fps but taking it from say 168 to 218 fps in CoD-MW doesnt really make ya notice things
Love this advice, but...do you think I need to upgrade my MoBo?
I was thinking about doing either the dual 570s or waiting for the new 7950 that everyone's clamoring about, and upgrading my CPU to the 2500 or 2600. I'll get more RAM to 8 or 12 GBs, but consider that almost an afterthought. Same 750 Corsair PSU.
(I don't necessarily want to remove my MoBo and reinstalling it as I've been out of the game for a little while. )