Is it a good idea to crossfire a R9 290 and R9 290x on a single display unit? If so, what amount of power are we talking about from the PSU here?
Hey there Sohaib,
This is a great question, and something that's easy to answer, but it really depends on the resolution of your display. If you are running a 1080p monitor, a single Radeon R9 290/290X would be enough. For a 1440p display at 60Hz, the same applies. But if it's a 120/144Hz monitor, then a second R9 290/290X would definitely be put to good use depending on the game.
If you're running a 4K monitor, then a second R9 290/290X would definitely be something I'd recommend for performance, but for power consumption and what AMD has coming soon, I would not recommend it. If you've already got a single R9 290/290X and were going to purchase another - I would keep your single card as it will be good enough for your display.
As for power consumption, a single R9 290X consumes around 450-500W of power. A second card can bump this up to ~800W or so, and with overclocking, you could easily reach 1000W or so for a pair of 290X's in Crossfire. Our last review looked at the SAPPHIRE Radeon R9 290X 8GB Tri-X, which consumed 450W in Battlefield 4, and while overclocked, a huge 625W.
AMD is close to releasing their Radeon R9 390X, which should provide much more performance, all while using similar, if not less power than a R9 290X right now. My advice, would be to stay where you are with the single card and wait it out, or upgrade to the R9 390X when it's released.