I'm not sure why Comcast doesnt offer a discount to customers as an incentive for letting them use the router as a hotspot. Comcast took a situation that could have been win-win and turned it to lose-lose.
I think the best comparison you will be able to make in reviews will be GTX590 vs GTX970. Overall performance of GTX570 SLI vs GTX590 would be pretty similar, it's still not a perfect comparison but it's a place to start:http://www.anandtech.com/bench/product/1185?vs=1355
I would say no, plus your getting more benefit going to a single current generation card - more vram, less power consumption, no SLI issues. You need to decide if that is worth it to you, since it's a $100 upgrade vs a $330 upgrade.