cramved :
socialdarwinist1 :
Depends somewhat on what monitor you're talking about, but a GTX 670 ought to be able to run just about every modern game at 30+ fps on 1440p if you turn off MSAA/SSAA. I would personally go for the 1440p (I recently bought a Dell U2713HM on sale and it's been fantastic), especially as there's a good chance the monitor will outlive your video card by at least a couple years.
I was thinking about one of the Korean monitors for the 1440p because I am reading that they are pretty good.
And is a 650 watt psu big enough to add another 670?
I don't know how much you've looked into the Korean monitors. I'll give you a brief rundown just in case you're not familiar (apologies if you've already looked into this already): essentially all the modern 2560x1440 panels are Korean. Dell, Asus, etc. buy these panels - but they will only buy panels rated A+ or A. These panel ratings depend on a number of variables, but essentially A- means overall lower quality. That said, plenty of people have had good luck with these panels (few dead/stuck pixels, acceptable backlight bleed, etc.). They do have shortcomings, however: if there's anything wrong, good luck with an RMA - not all sellers are terrible with this but if nothing else, shipping a monitor back to Korea is going to be expensive. They also have much looser policies on total acceptable dead pixels, panel uniformity, etc. You're also probably looking at more limited inputs, a fixed/cheaper stand, no monitor-specific picture adjustments, and so on. I went with a Dell for peace of mind and for the adjustable stand, but it seems a number of people have had excellent luck with the Korean monitors. A number of different models are capable of overclocking up to and beyond 96Hz, which means you reap the advantages of frame rates in excess of 60. To me, this would be the most compelling reason to choose a Korean monitor.
TL;DR - Korean monitors are a bit riskier and lack the features, but are cheaper and some can be overclocked to a higher refresh rate.
As for your power supply, so long as it is a solid 650W (and is actually capable of handling 650W), you should be fine to SLI the GTX 670s. I'd recommend checking out pcpartpicker as you can choose all your components and it will give you an estimated wattage usage for your whole system.