anyone here SLI 2x 970gtx?
Debating whether to jump to 10 series or SLI the 9 series.
Not me. Never done it or tried it.
It probably really depends on (hopefully) how cheap you can either get two 970's for; or if you already have a 970 already and can get another one dirt cheap. If you can get it ultra-cheap - yeah, might be worth a shot to SLI.
Otherwise, eh - I'd probably rather go get a new card w/ more VRAM; i.e. 6GB 1060, 8GB 1070, or 8GB 1080. While some games can push that 1080p at higher settings to 4GB of VRAM usage (Far Cry 4 + Batman AK come to mind) - it's really 1440p and 4K at higher settings that can eat up lots of more VRAM.
New list of SLI supported games -
http://www.geforce.com/games-applications/technology/sli
Old list of SLI supported games -
http://www.nvidia.in/object/sli-technology-games-in.html
If you are thinking of SLI'ing, you might want to grab NVidia Inspector (in case you don't have it) just in case there are some games you might be able to unofficially force SLI On with. Do some Google searches and find out on how to do it. I don't know how to - don't have 2 cards, never tried it.
Hopefully you got a bad-ass PSU to handle 2 of them 970's, if you're going this route.
My "meh" w/ SLI is while you'll improve performance on games + resolutions likely on games that SLI works with officially and/or those you can force it on w/ using NVidia Inspector, you still have some things to deal with. Not all games support SLI officially. Obviously, you might need NVidia Inspector to force it + learn Hex on how to force it on games that don't support it officially.
You'll still be limited to just ONE card's VRAM buffer count; in other words, you'll still be stuck 3.5GB VRAM buffer on the 970. So, if you have a game w/ 4GB or above higher-end graphical settings (like Dishonored 2, Doom 2016, SoM, etc) - eh, you're still stuck w/ that 3.5GB limit, even while doing SLI.
Also, performance is said that SLI isn't always exactly 2x's b/c you have two cards. Maybe, maybe not; it normally depends per game.