Upgrading from 6870

The performance of the GTX 660/Ti/670 ETC... is unknown as far as I'm aware, I would imagine that the GTX660 or Ti would be competing with the HD7870.

The GTX570's offer very similar performance to the HD7870 for less money so that would be my choice.

Make sure you have a high quality 500W or greater power supply.

 

If you were to trust the "leaks" of the kepler series, kepler would be the victor with at least a 20% performance margin   Thankfully, we all know these "leaked" benchmarks are bs (Though I honestly hope not). If you are really thinking about buying kepler, it should be released sometime later this month, nvidia has to answer the 7000s soon. From what I can see, the only adavantage the only advantage the 7870 has over a similar card like the 570 is less power consumption (im also going to assume cooler performance) and of course, a higher price   (with on average of 5% better performance than the gtx 570). In all honestly, keep your card until you see the lineup that kepler has to offer, so at least you can make an informed descision and actually SEE what your options are. AND if you don't like the 7000 or 600's, you can always buy yourself a 580 for dirt cheap after the 680 comes out