Ok, it's been an year now and I really can't figure this crap out, so as a last resort I'm asking for help. I've read long ago that there are severe performance issues with this combo, but I could not find a solution and if this is known for that long, there should be a bloody one. I get the fact the FX will bottleneck the R9, but I really don't expect it to fall down to under 10 FPS when I approach/enter station or even try to render planetary surface where things go completely bonkers for few seconds. I've tried it all - different drivers, overclocking, lowering ED settings - it won't make a difference. At least not one that's noticeable for long. To be clear here, my problem is most apparent when I approach/enter a station and approach a planet. Sure, I found supersampling affects it most, but I won't play with a setting below 1.0 and this is a huge compromise on my end. Currently my settings are a complete mishmash and I don't really believe this is the way I should be playing with my setup, especially considering it does not help a bit.
So, please lads, elaborate some ideas. Thanks.

So, please lads, elaborate some ideas. Thanks.