Single card or SLI/Xfire?

I have a GTX 760 and i just doent do what i need it todo, so i was considering upgrading to either, a pair of GTX 770s or R9 280Xs or a single GTX 780ti or a R9 290x, but im not sure which option to go with. Help me??

It really comes down to how much you're willing to spend.

I'm currently running two 7870's in crossfire and I would do it again if I were asked. I have had a few hiccups and some games don't really optimize for it well, but overall I'm very happy with the performance gain I got from crossfiring.

Just remember that if you SLI/Crossfire, you're going to need to make sure your PSU can handle it.

They cost around the same price where im from and i will be upgrading to a new PSU, mine is broken anyways, how did you 7870s scale?

im running two GTX 660s, they scale really well in some games up to 80 90% in tomb raider, but other games like metro last light I see around 30 - 50 % increase, but since they have some head room it really helps in the physx department so I don't get as many slow downs.

Thats not bad at all. 

I've just recently switched from a HD 7990 to a GTX 780ti because I was sick of the incompatibility issues of Crossfire and AMD in general. Whenever AMD releases a new driver there are always Crossfire issues, which leads you to disabling it entirely for certain games.

For instance the Battlefield 4 Mantle update. When the driver was released for that, they openly admitted that it didn't work correctly in crossfire setups and that it caused stuttering issues. The stuttering issues were  game breaking and made it completely unplayable. So I switched back to DX11 and waited patiently for them to fix it. Unfortunately they weren't in much of a rush to fix it and we all had to wait four weeks for an update which did not fix the issue at all.

I had similar problems in BF3 with this and Titanfall would not run with Crossfire enabled either. After a lot of deliberation I took the plunge and got my-self a single MSI GTX 780ti Twin Frozr and have never looked back. I absolutely love this card. I can easily run BF4 with it looking gorgeous and maintain 120 fps constant. I would recommend it any day of the week if you can afford it. 

Hope this helps

I'd upgrade to a single GTX 780ti, it will give you more FPS in more games without having to deal with bullshit SLi or crossfire scaling issues.

edit: But do you really need to upgrade? Stick with your 760 and wait for 800 series to be released.