So my previous system had two Radeon HD 7970. One died, ok whatever. Then following month second one died. Had no GPU, got a R9 270 to use temporarily while I build new system.
Anyways, ended up getting a second R9 270x. Difference between 270 and 270x is 30W TDP and 10% performance, according to internet. But they have same chipset, so can crossfire them.
So now my old system has 270+270X in Crossfire. I did Furmark, Unigine Heaven, Unigine Valley, and FFXIV Heavensward benchmark on it. (used Highest presets for each benchmark, and 1080 FHD preset for Furmark).