So I will be coming into some money soon. I am trying to decide between another 980Ti Classified for Sli or a 1080 Classified. I won't be buying another video card for a while after this decision. I already can practically run Arma 3 and get 60 FPS @ 4k as it is now. I hear SLI still doesn't work right. Thanks

In your shoes...hmmm
 
I would either go for another 980ti classy or wait until a 1080ti comes a knocking

A 1080 isn't going to be that much faster than a 980 Ti. I own both, and also did a lot of research prior to stepping up my old 980 Ti Classified (still have a 980 Ti G1 Gaming).
 
Yet if the games that you play don't support SLI then even the marginal 15 to 30% improvement is the better choice.

Sell your other classy and buy a pascal titan x. 

http://gpu.userbenchmark.com/Compare/Nvidia-GTX-1080-vs-Nvidia-GTX-980-Ti/3603vs3439
 
Based on the above report, and with 12,104 users that compared them, you will gain ~30% going to a 1080.
 
My opinion? Wait. Try and wait a year for Volta to come out. In a year the prices should drop some for Pascal if you can't wait any longer and need the extra 2gb of RAM.

 
1080 Classy. I have one, and love the card.      

If you can wait until January, then you could get a 1080 Ti.  I would highly advise against a second 980 Ti at this time.  I have two and multi-GPU support hasn't been worse than it is now.  Of the recent games I've purchased:
 
- Gears of War 4: No multi-GPU support
- Forza Horizon 3: No multi-GPU support
- Civilization 6: Extremely poor multi-GPU support (although it doesn't really matter)
- Battlefield 1: Terrible SLI profile.  I used a custom profile with the open beta, which worked much better.  The same custom profile is no longer possible.
 
I purchased a handful of other games this year and multi-GPU support sucks for the most part.  These are dark times for enthusiasts.  I would also advise against a 1080, since it's not a large enough upgrade.  The other option is to go for a Titan XP if you absolutely need to upgrade now.

gridironcpj
If you can wait until January, then you could get a 1080 Ti.  I would highly advise against a second 980 Ti at this time.  I have two and multi-GPU support hasn't been worse than it is now.  Of the recent games I've purchased:
 
- Gears of War 4: No multi-GPU support
- Forza Horizon 3: No multi-GPU support
- Civilization 6: Extremely poor multi-GPU support (although it doesn't really matter)
- Battlefield 1: Terrible SLI profile.  I used a custom profile with the open beta, which worked much better.  The same custom profile is no longer possible.
 
I purchased a handful of other games this year and multi-GPU support sucks for the most part.  These are dark times for enthusiasts.  I would also advise against a 1080, since it's not a large enough upgrade.  The other option is to go for a Titan XP if you absolutely need to upgrade now.

And all the people saying SLI is "relevant"? pfff... Looks like it's not when you see the latest game(s) have no SLI support.

stalinx20

gridironcpj
If you can wait until January, then you could get a 1080 Ti.  I would highly advise against a second 980 Ti at this time.  I have two and multi-GPU support hasn't been worse than it is now.  Of the recent games I've purchased:
 
- Gears of War 4: No multi-GPU support
- Forza Horizon 3: No multi-GPU support
- Civilization 6: Extremely poor multi-GPU support (although it doesn't really matter)
- Battlefield 1: Terrible SLI profile.  I used a custom profile with the open beta, which worked much better.  The same custom profile is no longer possible.
 
I purchased a handful of other games this year and multi-GPU support sucks for the most part.  These are dark times for enthusiasts.  I would also advise against a 1080, since it's not a large enough upgrade.  The other option is to go for a Titan XP if you absolutely need to upgrade now.

And all the people saying SLI is "relevant"? pfff... Looks like it's not when you see the latest game(s) have no SLI support.

Multi-GPU support has gotten much worse lately.  The irony of a PC gaming boom is that the share of multi-GPU systems has decreased, yielding less "poops given" from Nvidia and developers.  It was great a few years ago.  Now, it's as if I only have one 980 Ti instead of two.  I sort of NEED that extra horsepower at 3440x1440 for a lot of these games if I want to hit 100FPS.

Sajin
Sell your other classy and buy a pascal titan x. 

I very much agree and would like to add, you will grealty benefit if you have water cooling be it an AIO or custom loop