Should I Crossfire my 7970 or go for a 780?

Crossfire isnt that efficient so I say 780ti.

Check your MB manual to be sure the slots you want to use are both X8 bandwidth. The board's web site doesn't specify. However, it does say the last slot is only x4.

EVGA GTX780 (967MHz base)

Crossfire still has a ways to go, nor is SLI perfect either. There are still stutter issues, nor is Crossfire working in DX9 last time I checked (2nd GPU runt issues resulting in both stutter and 30FPS perceived frame rate not 60FPS).

It's not as simple as looking at the benchmarks.

Additionally, the GTX780 has three great games:
http://www.anandtech.com/show/7430/nvidia-announces-holiday-geforce-game-bundles

Shadowplay: records 1080p 60Hz (I never dropped my frame rate at 78FPS VSYNC OFF to test).

PHYSX: not a huge deal maybe, but you are missing something in games that can't play it. I turn it off in some games though.

G-SYNC: this is a GAME CHANGER, so I advise you to WAIT on your monitor if possible. http://www.anandtech.com/show/7436/nvidias-gsync-attempting-to-revolutionize-gaming-via-smoothness

G-Sync is NOT a minor thing. I studied computer and I can tell you it's simply awesome. For example:
"Next up was disabling v-sync with hopes of reducing stuttering, resulting in both stuttering (still refresh rate/fps mismatch) and now tearing. The G-Sync system, once again, handled the test case perfectly. It delivered the same smoothness and visual experience as if the we were looking at a game rendering perfectly at a constant 60 fps. "

2560x1440 vs 1920x1080:

I have a 1440p (many have issues BTW), but I actually game mostly at 1920x1080. Why? Because the difference in many games is next to nothing but with a 30% frame rate hit. If you are at 60FPS VSYNC'd a better card can also produce less stutter; it's a misconception that all 60FPS VSYNC'd experiences are the same.

I play Starcraft 2, Torchlight, Dragon Age and several other games at 2560x1440. Basically small HUD/TEXT which looks a lot better at 2560x1440. I can also maintain those at 60FPS anyway.

But Crysis 3 at 2560x1440? Better than 1920x1080? Only if you're looking really close and even then you wouldn't likely notice during a game.

I have an Asus GTX680 DC2U (comparable to an OC'd 770) and I've played pretty much every game. I tweak to maintain 60FPS (50FPS in Crysis as it's supported). The quality difference between what I can maintain and the absolute BEST isn't really that huge, and with a single GTX780 you'd do better.

I hope this is useful.

Summary:
- EVGA GTX780 (967MHz base) $500
- 3 games
- PhysX
- Shadowplay
- G-Sync
- 2560x1440 vs 1920x1080.

Some people have short-term/selective memory and forget the days when the 7970 was being sold for $550-$600; and the GTX 680 was cheaper and faster than the 7970; and then a year later when the GTX 770 was cheaper and faster than the 7970 GHz.

Now that I see you are playing Skyrim, then Crossfire should be immediately ruled out, and AMD cards in general as well. Crossfire frame pacing does not work for DirectX 9 games, which means that dual AMD cards will only give the performance of a single card (i.e. a waste of money).

In general, Skyrim performance favors Nvidia cards. But another little known fact is that Skyrim fundamentally looks better on Nvidia cards. Only Nvidia cards allow you to enable Ambient Occlusion in Skyrim, which effects nearly everything in game as it improves shadow quality, realism, and depth. In the image below, Skyrim on AMD cards looks like the "AO: Off" screen:


http://www.geforce.com/whats-new/guides/the-elder-scrolls-v-skyrim-tweak-guide#19

g-sync is going to be MASSIVELY EXPENSIVE

It seems like nvidia guys loved getting ripped off. I don't get it. They must get good allowances.