The not enough ram cutoff point is not 1920X and is higher than 5760x1200.
" While gaming at 2560x1600 was fantastic, we wanted to push the video card to its limits, and so next we configured an NV Surround triple-display configuration and gamed on three displays from the single GeForce GTX 680. We wanted to be able to run at the native resolution of 5760x1200 and compare the performance to the Radeon HD 7970. We figured if any resolution is going to show the advantages of AMD's memory capacity and memory bandwidth edge it would be 5760x1200. We were absolutely surprised that the GeForce GTX 680 had no trouble keeping pace with the Radeon HD 7970 at 5760x1200. We thought this is the resolution we might see the GTX 680 bottleneck, but to our surprise no bottlenecks were experienced. "
Note the 7970's extra and useless 1G of ram doesn't prevent the 0 frames in Skyrim and doesn't prevent it's loss to the 680 @ 5760X1200
BF3 same resolution same cards:
" We found that both the Radeon HD 7970 and GeForce GTX 680 were playable at 5760x1200 with "Ultra" settings and FXAA, as long as we reduced Ambient Occlusion to SSAO. With the default, and highest quality option, HBAO enabled performance was sluggish and laggy on both video cards at this resolution. HBAO caused a severe performance penalty. When we reduced the quality down to SSAO, performance picked up and the game was playable. There is a slight performance edge towards the GTX 680."
So, there's no more room for ram to improve anything, the cores are already eaten up, the 7970 core fails before the 680, slightly...
If there isn't a faster core ( like a huge LN2 overclock ) ram can't help. Proof is everywhere - when we get faster cores that immediately changes, of course.
Perhaps if one has some massive multi core server board with a 16X slot it could push enough.