690 vs 780

Found a 690 for $725. Do i get it instead of a 780?

The 690 is essentionally two 680's on one pcb. So it should be better. But what comes with it is more power consumption and more heat.

look at the games you play and see if they are good with sli or if a single card is better in your games.

The 780 is cheaper and gives you all the performance you could need at 1440p, with a lot of stability and more Vram for mods. I wouldn't trust the 690 for Skyrim mods, with all the Vram issues that are found in the 6xx series. I do acknowledge that the 690 will deliver a higher performance value, but I really do feel the 780 is the better all-round choice.

I actually get 60+ FPS in 9/10 games that I happen to own. That's with max AA and ambient occlusion, plus other post processing. Metro 2033 was playable with every possible enhancement turned on, and the most demanding enhancements chosen. Only one part of the game dipped below 30. DayZ also happens to be quite demanding, I can make it very playable by adjusting one process.

If you're gaming at 1080p, get a 770.

Run with the 690. 2 680's > 1 780- the 690 is, after all, effectively an Nvidia SLI solution built in to a single PCB, and it's certainly bound to be faster than a single GPU card which is marginally faster than either one of the single cards.

Two 7950s would be cheaper, that'd be a good alternative to consider. That's probably one of few options I would choose, personally.

There aren't as many issues with crossfire these days, they've been fixed. You've got the 3GB of Vram "sweet spot", which would help at 1440p.

I believe you're using the PB278Q? That monitor has a 60Hz refresh rate, which means you won't see more than 60FPS. My 780 hits that wall quite frequently. You don't need anything more. But the 7950 is arguably the best value, certainly beats the 780.

I'd go with the 780 because its the fastest single card out there right now. Single cards are much more trustworthy, and there are instances where the 780 beats out the thousand dollar Titan. 

Having gone through 680 SLI, I ended up going back to single card and selling my other 680 because it was a lot less hassle and I wasn't skimping out on 1080p performance. 

If anything, go 780, or 770 with 4gb. Happy hunting!