Woof. R9 290x by itself is recommended 650w psu. R9 290x CF is recommended 1000w although a solid quality 850w is usually sufficient minimum. Add loop needs on top and thats getting into highly expensive psu ranges. Overall a gtx1080 by itself is equitable to the CF, when the games have sufficient CF support. Anything less and you can kiss that fps goodbye, and more than a few games are so miserably optimized for CF you'll actually have stuttering issues and severe fps drops, ending up with worse playability than a single 290x is capable of. A single 1080ti will top anything that CF is capable of, without the issues, capable of 4k gaming with its full 11Gb of vram, vrs the 4Gb/8Gb possible. If those are the 4Gb version of the 290x, the vram will be closer in ability to a 3Gb nvidia card, which is dismal for higher resolution capability.