I need a new graphics card

As you can tell by the system specs below my post, my current graphics card is bottlenecking my system. I just picked up Guild Wars 2 today and I'm only getting like 15 fps on max settings.

So, yeah, I'll be needing a new graphics card, and I want to stick with NVIDIA since that's what I've always used. I'd prefer just to get a single card for now, I'm not familiar with SLI and don't want to have to go through the trouble (and double the price).

I definitely don't want anything more expensive than the GTX 680 (which seems to go for about $500-670, depending on whether you get the 2gb or 4gb one)

So I have a few options:

GTX 680 4GB - $570-670
GTX 680 2GB - $500-550

GTX 670 4GB - $480
GTX 670 2GB - $380-440

GTX 580 3GB - $430
GTX 580 1.5GB - $350-370

GTX 660Ti 3GB - $340
GTX 660Ti 2GB - $300-320

GTX 570 2.5GB - $320
GTX 570 1.25GB - $260-340

GTX 560Ti (448 cores) 1.25GB - $240-300
GTX 560Ti 2GB - $280
GTX 560Ti 1GB - $215-250

GTX 480 1.5GB - $230

And I have a few questions about my options. First of all, according to the ratings chart here on OCN, the performance of a card doesn't seem to necessarily correspond to its price or its release date. For example, the 560Ti (rank 34/35) is below the 480 (rank 25). This is even more true in this other chart, where the $1000 GTX 690 ranks 7th. I'm not sure what to make of these charts.

Secondly, what's up with the GTX 590? Everywhere I look it says it's either discontinued or out of stock, yet apparently it ranks better than the GTX 680, according to the OCN chart.

Also, will all of the cards listed allow me to play games on the absolute max settings (at 1980x1050 resolution) at 120fps for at least two or three years to come, given my other hardware? If not, which of these cards will provide that for me? Or am I being completely unrealistic in expecting any graphics card to provide 120+ fps under all circumstances on max graphics for all current and soon-to-come games?

And finally, will my power supply be able to handle any of the above cards? I know nothing about power supplies at all...

Thanks!

Sorry, I just updated my sig monitor. It is a 120Hz monitor.

I haven't reformatted my computer in forever, and the hard drive is like 90% full (not sure if that would affect game performance), and I play with ~1GB of background programs, but that still leaves 5GB of RAM for any game I'm playing, so I don't know why background programs would be a problem.

Also, I'm not just concerned with running GW2, and also not just concerned with being able to run it; I want to run games on max graphics with very high FPS, and I want to be able to do so for games that are more taxing than GW2, even games that are coming out in a couple years.
Edited by Aelius - 8/28/12 at 8:18pm

Does the GTX 680 (2GB) not offer much improvement over the 670 to justify the cost?