3840x1024 Eyefinity
Well, it's not so much that you'll see a performance "boost" as it is that you'll avoid a performance nosedive. At such high resolutions, some games/settings will just cripple a 1GB card because it doesn't have enough framebuffer, and you'll run at single digit framerates.
Extra vram just gives the graphics card more space available to store the data that it needs to work with as it renders objects. Having more of it cannot help performance, but if you run out of it then your performance will completely crash as the GPU will start having to store fetch data from elsewhere than its own memory.
I'd consider a powerful 2GB GPU a must for eyefinity setups. If you're planning to run 3 screens for games, I'd view a 6950 the absolute minimum GPU to consider for a purchase. If you build around eyefinity, expect to sink a decent amount of money into your graphics card OR to not play at very high settings or to not play at very smooth framerates.
I'd say get the 2100 and Black Friday UGGs On Sale 6850 and just play on a single screen. If you want to do 2013 Black Friday UGGs On Sale Online - UGGs Store eyefinity, I'd recommend a 2500k + 6950 (or even a better GPU) and it doesn't sound like you want to spend that much money.
If you are OK with lowish settings on games, get the 2500k + 6850 for eyefinity and then upgrade your GPU in another year or two when you are unhappy with the settings it can handle.
How does the processor's impact on performance scale with screen size? In both of the Eyefinity focused setups you recommend, the CPU is blackfridayuggsus.com a i52500k.
Any particular reason for this?
Is an i32120 simply too weak to handle such a high resolution at highish (not ultra) settings?
I understand that paying almost double for a better processor is going to yield much better performance and that the i52500k can be OC'd on top of that and therefore it will last me longer into the future. but is there something else I'm missing that the i52500k offers for Eyefinity?
Thanks again for your input, you answered my curiosities perfectly.
I just think that the 2500k will last longer as a good component than either the 6850 or 6950, that's why I made the recommendation (also, I saw starcraft 2 in your list of games, which likes lots of CPU horsepower).
The i32100 is fine to handle such resolution in fact, as resolution increases, the stress on your CPU decreases because you become more and more limited by your GPU instead.
Only reason I recommended the 2500k was so that it would be longer before you needed a CPU upgrade. To me personally it is easier to upgrade the graphics card than the CPU. The i32120 is certainly a capable CPU, however. Nothing you're missing, it was just a recommendation based on my own preferences.