I think your psu will not handle 2x gtx 1080ti, but i think it can handle 2x gtx1070ti.
And my guess this gpu will be your best bet. imho.
Thank you. That's a helpful start.
Would it make sense to upgrade my PSU to be able to support 2 1080ti?
Which manufacturer would you recommend? There are many different 1070ti. I am partial to the 3 fan look, but really am not that knowledgeable about parts overall.
Two 1080ti (Asus Strix 3 fans) consumes 600W (one is 300W) at max overload + rest of the PC (150W) = you need at least 850W PSU (recomended 1000W)
Two 1070ti (Palit SuperJet stream) consumes 360W (one si 180W) al max overload + rest of the PC (150W) = you need at least 650W PSU (recomended 850W)
Corsair is always best choice, some series have 5, some 7 years warranty. I prefer RM1000x (i have them on all my rigs, some rigs with one and some with two)