sgminer.exe -k darkcoin -g 2 --thread-concurrency 8192 --gpu-memclock 1375 --gpu-engine 1080 --gpu-powertune d --auto-fan --gpu-fan 50-100 --temp-overheat 75 --temp-cutoff 85 --intensity 13
1.8mh on my 7950's.
Browsing, movies, games (although it decrease a little bit if, 1.5-1.6, I start a game i.e. PoE) and don't feel it at all.
Anyways just wanted to give another specc.
But like someone said previously. Should try and play a bit to find the one that works good for you.

Why are you using a 280x's tc? 7950s should either have multiples of 1792 (shader count).
Anyway you seem to get better perf than me, the main difference is gpu-engine, might try to up it a bit.
On a related note, i'm mining on
https://hic.crunchharder.net/ but the dashboard is all over the place, not being up to date with blocks and showing 0 shares for me even though my worker is mining(even according to the site dash itself) and sgminer registering tons of accepted.
Anybody else having the same prob?