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.
dont get me wrong -- when building my first rigs, i covered a few years back of this thread and learnt a lot from posts of rigs by builders, owners etc.
As a newbie, I have reached to some of them, with the design I had in mind and many have help me and share their experience etc.
I understand that they are many considerations, especially on how to optimise performance, cooling, voltage etc. No hard and fast rules there.
So in conclusion, many different angles, strategies, purpose for every build of rigs and even ASICs mining topics.
This thread have many good examples of information sharing and creativity from forum members, all done in good faith and appreciation - let's promote that.