oooh thats going to be a tough one, I think. Here's why, that ASUS 1070 STRIX OC is a BEAST and can GPUBoost itself past 2Ghz EASY, almost all the time and it stays VERY COOL. (I know because I had one before on my Full-Tower ATX build and I sold it like 4 months ago on eBay for like 390 shipped to help with my S4 mini, it was a BEAST) He's going to have to be okay with it not being as cool running or as good of an overclocker, so he might see a few percent FPS drop (5% at the most).I know a couple of you guys have done a 1070 mini in your S4. Any particular card you recommend over the other for my husbands build? He currently has an ASUS 1070 Strix 8 GB OC.
I'm not familiar with the 1070's but you might want to go with the GALAX 1070 mini? I heard it has a stock PCB so you dont have to mod the DC/DC connector going out of the S4 Mini.