Scaling works very well on this game with 970s in SLI. I have the lower performing 970m in SLI in my laptop, and the game is hovering at 59-60 fps avg with 54-55 min. See the setting I use in my response to Robb213's comment. I was also considering 970s for a desktop build, they are great cards.
Thank you! Also they are great cards for a desktop build, maxed out everything so far @3440x1440, struggles slightly with hairworks turned on though in the whitcher 3 and with shadows in fallout 4 (though I think they fixed that because it seems a lot more stable now)
The biggest thing holding me back is that its a laptop, and has the problem of thermal throttling. The CPU is an i7-4870HQ and clocks at about 3.6 Ghz, I think the CPU is the bigger thing holding back performance. 2 970's is more than enough, especially if they have more than 3GB VRAM. I agree with the comment about Direct X 12 and Pascal. If there was an update for the game that allowed DX12, the VRAM would double in SLI and give you 6GB if you had 3 per card, or 8 if you had 4 per card. DX12 is the cheapest way for us all to get some extra frames. And when pascal comes out... chips designed specifically for 4K gamers in mind.
Desktop 970s in SLI are amazing if they can pull off those fps numbers at 4K, I didnt read that you were playing at 4K resolutions. That's incredible.
Update: I benchmarked in Soviet Installation to judge the impact on a high-end gaming laptop using SLI
Test System Specs:
Aorus X7 Pro 3rd Gen (before G-sync) with some upgrades
Intel i7-4870HQ ~3.5-3.7Ghz
SLI 970m 3GB GDDR5
Raid0 mSATA SSDs / 1TB Samsung Evo SSD
32 GB DDR3 1866mhz RAM
Repaste CPU & GPUs with Arctic Silver 5
1080p
HIGH Tex quality
VERY HIGH everything else
x16 AF
MSAA
Avg. 60fps
Min-43 fps
4K/3840x2160
LOW/MEDIUMTex Quality
Antialiasing OFF/ Anisotropic Filter TRILINEAR (not needed at these resolutions)
Low/Medium most settings
PureHair Very High (cause why would you want to play without it?)
Avg 30 fps
Min 20 fps
I consider 4k unplayable on a laptop, since I wager 980m SLI to net you maybe 10-20 fps extra?
1080p at the above settings looks incredibly good. I'll wait for Pascal to build another Desktop.
I am still trying to decide which cards will nail a game like this at 60fps Min and maxed out at 4K.