Your choices are fine. When it comes to selecting GPU, the choice, between your 3 is slightly complicated. It does depend on what game you are playing. I see you like Crysis. For that, the HD7950 is the best performer. Of the other two, whilst the HD7870, whilst it doesn't perform quite as well as the HD7950, it could be considered better value for money. Obviously depends on prices etc, where you are. If, on the other hand, you are playing BF3, or Shogun, the GTX 660Ti is the best best. Unfortunately, it really is a case of looking at benchmarks, on a site like anandtech, for the performance in the games you want to play, and looking at the prices, to see which, FOR YOU, is the best value for money.
There are some wildly different benchmark results, depending which site you get them from.
Anandtech: 1920x1200 Ultra FXAA-High BF3
GTX660Ti - 81.7 FPS
HD7950 - 62.7 FPS
I think a lot of it is down to certain test rigs favouring nVidia, some Radeon, plus exact settings.
Battlefield 3 is known to be optimized for Nvidia cards. Fact is, that more often than not, the 7950 is superior to the 660 TI, so is the lesser 7870 for that matter.
As far as reviews that vary from site to site, check the test setup page and see what driver version they're running AMD Catalyst 12.7 is the most recent, and its the one largely responsible for putting AMD 7xxx series cards ahead of Nvidia's 6xx series.
Does Physx play an important role in games ??
Not really, theres about 5 games that actually use it that anyone really plays. Theres a list on Wikipedia, I don't know how complete it is, but its a rather minor eye-candy detail. http://en.wikipedia.org/wiki/Physx
"Much like we saw at 2560x1600, even at 1920x1080 with 4X MSAA the GALAXY GeForce GTX 660 Ti GC 3GB overclocked video card is very close to overclocked GTX 670 performance. The overclocked GTX 670 is only 6% faster than the GALAXY 660 Ti overclocked video card. What's more, the overclocked HD 7950 and overclocked GTX 670 are neck and neck in performance at 1920x1080 with 4X MSAA. Despite the HD 7950's large memory bandwidth difference, they are still the same performance in the end."
"In Skyrim once again we are surprised how the overclocked HD 7950 takes the lead in this game. The GALAXY GTX 660 Ti GC 3GB overclocked video card takes the back seat, but performance as you can see is consistently over 60 FPS even at 1920x1080 with 8X MSAA enabled. Though it is technically slower than an overclocked GTX 670 or HD 7950, you can't argue that an average of 77.8 FPS with a minimum of 56 FPS is bad for 1920x1080 with 8X MSAA enabled."
Hmm. 12.8 drivers for Catalyst already? Whats with these people always saying that AMD is blah blah slow at updating drivers? lol. I haven't seen an update for my 550 TI in months.
Anandtech is probably using the same drivers because they're not running new benches, they're just copy and pasting over benches they've already done. Pretty half-ass. I can't say that I blame them though, I doubt theres much of a difference.
The advantage with Anandtech is that you can do a quick comparason between ANY pair of REFERENCE cards on the same bench, same methodology. Something you don't always get everywhere. The disadvantage is they're obviously not done on same date, so not necessarily with TODAY'S drivers. I don't know how often they "refresh" their tests.
Will the HD7870 play most games well at 1920x1080, with high settings - Yes. Max out? If that were the case, "better" cards would be pretty pointless. As to upcoming games? Give me a crystal ball, and I might be able to tell you. Couldn't say that for even the HD7970.