PC Help, Crossfire setup not performing

Hi there awesome community, a little help :) For my first gaming rig, I went for Sabertooth 990FX mobo, AMD FX 8370, 16GB of DDR3 @ 1866 RAM, 2 x R9 390x GPU (Crossfire). Power supply is the Corsair RM1000. I have updated all the drivers, yet I don't get anywhere near the performance many others get on the R9 390X. Temps & everything seems ok. I have 2 SSD for OS, one for games, and 8TB Seagate for other data. The FPS in games drops from say 100 to 15 and is making the video games I play unplayable, quite depressing really lol.

I am only running at 1080p nothing special but I rarely get a solid 60 Fps lock, will get dips to the 20s. Tried it at first with just one R9 390x with no joy. Having spent all that I didn't want to buy new mobo and CPU. Overclocked CPU ( running at 4.4Ghz) and GPU's ( not much as they already are OC's). Having come from PS4 & XBox1 I was hoping to have my mind blown, but so far after spend £1300 I am feeling pretty jipped.

Any advise??

I would go back to using one card for starts because throwing another card at a system where the first card isn't working properly isn’t going to help. I would then take off any over clock on you gpu just for troubleshooting purposes. I would also check the temps of the gpu maybe its thermal throttling. I would then go about reinstalling the driver purge the drive first of coarse then reinstall. I would also make sure that the card is properly slotted on the motherboard and make sure its on the fastest pci-e slot.

What are the cpu temps? Are you running a special cooler other than the stock? What does the cpu utilization look like when your playing games?

Your cpu will be a huge bottleneck definitely at 1080p.
However fps drops all the way down to 15fps shouldnt happen.
How does the setup perform with just a single 390X?
Do you get any massive fps drops then aswell?
Just to determine if it might be something related to the system.
Or that it could be something related to the gpu´s and or drivers.

Also which motherboard do you use?

What OS ? Yup ? Pc gaming is bit more technical. Fully updated drivers, regular maintenance on your pc, learning how to build and configure your pc correctly, keeping malware and viruses at bay. Judging by the build i would say thermal throttling might be a concern. You have to have a well build case for airflow or watercool. You migh even consider stepping up to 1440p or 4k with the way Amd likes to run 1080p.