"2GB SLi 670 owner chiming in here. Performance at 1440p is a dream, and I haven't noticed any issues with the VRam so far (not that you should take anecdotal information as fact, I just haven't seen any benchmarks that don't back up my own experiences).
I'd really like a solid explanation (or attempt) at why more VRam would/could make a difference for higher resolutions. Higher bandwidth, sure (which is why AMD excel at higher resolution -- something to consider if you're not too loyal to nVidia, though a lack of blower coolers isn't great for multi-GPU), but why higher VRam? It's obviously not the case now, so why would it change so drastically in the next couple of generations (yes consoles will have quite a bit of VRam, but that's shared with the actual RAM too -- and I wouldn't want to base my purchasing decision of pure speculation like that anyway). Are the texture files bigger? I don't think so, right? Is the frame-buffer any more than a couple MBs larger?
I'd go for the 770 if it were me. Even if VRam ever became an issue, I'd imagine the 2GB 770 would still be faster than a 4GB 760. It wouldn't become an issue over-night either. It's not like you're going to wake up one morning and 2GB is suddenly causing 30 FPS in all your games... The amount of VRam might slowly creep up as next gen console games become more developed, but like I said it's not going to be an instantaneous process (unless every game get's re-written all at once), and as such I really don't think it should be a problem within the lifetime of a 770 (again, speculation, but based on benchmarks rather than what we imagine games will be like in the future).
If you're planning on SLi, I'd recommend going with blower style (EVGA) coolers. This prevents the top card from becoming a furnace."
Here's my build. No overclocking or gtx 780
PCPartPicker part list:
http://pcpartpicker.com/p/BbJQcf
Price breakdown by merchant: http://pcpartpicker.com/p/BbJQcf/by_merchant/
CPU: Intel Xeon E3-1231 V3 3.4GHz Quad-Core Processor ($247.98 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: Gigabyte GA-Z97X-SLI ATX LGA1150 Motherboard ($118.99 @ Amazon)
Memory: G.Skill Ripjaws X Series 16GB (2 x 8GB) DDR3-1866 Memory ($162.99 @ Newegg)
Storage: PNY Optima 240GB 2.5" Solid State Drive ($92.98 @ Newegg)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($79.99 @ NCIX US)
Video Card: EVGA GeForce GTX 770 2GB Dual Superclocked ACX Video Card ($296.98 @ Newegg)
Case: Fractal Design Define R4 w/Window (Black Pearl) ATX Mid Tower Case ($79.99 @ Newegg)
Power Supply: EVGA SuperNOVA NEX 750W 80+ Gold Certified Fully-Modular ATX Power Supply ($79.99 @ Newegg)
Operating System: Microsoft Windows 8.1 - 64-bit (OEM) (64-bit) ($95.98 @ OutletPC)
Keyboard: AZIO KB506 Wired Standard Keyboard ($29.99 @ Amazon)
Other: Qnix 27" ($289.99)
Total: $1605.83
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-07-25 09:13 EDT-0400
You might want to go for sli gtx 760 or 770 instead of that 780.