You can mine Ether with AMD 280X or 380(X) with 4Gig mem.
Someone mentioned in another thread that the 380X is slower mining ETH than 280X. Seems most brands have higher core clock than 280's, but slower/narrower memory.
I use AMD 280X and GTX 970 (Strix from ASUS).
The GTX-cards are much more noisy, the power draw about the same as 280X,
but the nvidia-drivers are more stable than amd drivers.
Everyone's experience is different, but I agree with instability of AMD drivers on linux. I gave up on an old 7000 series a year+ ago because of the pain/upkeep involved. Rolled a gaming box (ASRock mobo w/EVGA 970 SSC), and since it was Win7 gave mining a try for kicks. Even though I hate windows it worked a lot better than expected, and was very stable. The EVGA's are quiet; "silent pc" fans on the case are louder than they are. Turns out Genoil's ethminer/cuda works well enough and is rock stable that I added another card (for SLI gaming, of course
).
But be prepared to baby-sit your rigs as ethminers are unstable.
Windows is out as well due to its builtin unstability, long install time and licence cost..
At least if you have newer motherboards then Win 7 is out as it may not recognize newer NICs.
I have heard Win 8.x is better at recognizing HW and installing correct drivers for it, but YMMV.
Not my experience at all (win/cuda miners). Unfortunately cuda-based devs are more oriented/plentiful on windows, so... Component drivers are provided by vendors, no need to rely on mr. softie. Linux can sometimes be iffy though...
Hashrates ETH: 280X ~ 20MH/s @ 1000/1500, GTX 970: ~ 16MH/s @ stock clock
Total system power draw w/dual 970's is 270W, getting 36MH without o/c (but the card is factory o/c'd anyway). Losing a few MH/s to save a decent bit of juice.
So far, a solid two weeks of 95% mining/5% gaming without a hitch (or reboot, if you can believe it). RHEL/CentOS is my pref distro because of work, but compiling eth miners (dependencies) is too much of a pain. If anyone has successfully run an ethminer on Linux Mint I'd give that a go...