R390s are reputed to be best for high resolution gaming modes, versus the Nvidia equivalent GTX-970 which is another badass card for mining - so there
are active fans, VRAM up to 8GB etc to consider, etc... all these will require more wattage.
A fury is much better at 4K plus. It is also more efficient.
There is a altcoins mining thread. Keep that in mind.
king_pin has contributed a lot to this thread. You should look and read through the tread if you don't recognize him (assuming he could be wrong). I interpret his post as a warning to new miners, based on his experience. I can tell you from my own that mining in the summer, or running many rigs in the same room drastically changes how your rig will run.
For pure cost effectiveness a 380 is the best new card to buy. Adding a single configuration setting will allow it to mine ETH at 20mh with stock freqs and the card costs ~$200. At stock freqs a single 380 should use ~170 watts. This is much more efficient than OC'ed 390's.
My 2 380s run at about 20-20.5, but oc. at stock (XFX 4gb) they run closer to 18. what config are you talking about ? I have the usual --cl-local-work 128 --cl-global-work 16384 --cl-extragpu-mem 0 and farm recheck 200. For some reason I cant input cl local work 256, maybe someone can tell me why, that would be nice. mining off stratum proxy - ethminer.
As for the eth rig pics, are you using non powered risers for 6 cards ? idk I'd be worried. I think the usb risers are worth it.
Also; IMO Sapphire is the best brand.