With your build, 3DMARK with FireStrike Extreme.
https://www.futuremark.com/support/downloads
Since you're running ASUS overclocked cards, you'll also want to get ASUS GPUTweak II, not so much for the overclocking, but for turning the fans to a very aggressive state. The default setting is very conservative and will let the GPU reach much too close to its upper heat range before playing catch-up:
https://www.asus.com/us/site/graphics-cards/gpu-tweak-ii/download/GPUTweak2_Ver1452.zip