Okay so I have recently taken a shine to the little NUCs and Brix, I am tempted to have one if they are still around in a few years, and what better to get a decent mSATA and 16GB RAM into this little beast and run linux, and make it into a gaming PC.
Okay so you will need to add your own RAM and mSATA or 2.5" SSD here, so get something fairly powerful, I recommend the 840 Evos, just use windows 1st to update the firmware then remove it and install linux.
Distro is completely up to you, I seem to finally be getting a long with openSUSE, so I would go with that, but something maybe like Linux Lite, or Lubuntu or Sabayon or Manjaro, or maybe even gentoo, go nuts! SteamOS would also be a nice option ;)
Also with 16GB RAM, dont bother with swap it is not needed with anything over 8GB RAM really, I never bother with it, all swap does is swap data from ram to your SSD/HDD now this is a bad thing in cases of SSDs, it will shortern the life of the SSD due to writes.
Get a decent keyboard/mouse and monitor, use a vesa mount it so need be, I personally would not, maybe get a dac also, all good then ;) a little PC that just because a pure monster.
Now dont expect to play games as high as your main gaming PC, but really. linux games dont take much power really, thanks to openGL over DX we get better framerates, then with the kernel we get better performance from our hardware, under more intense loads, you get everything better, so harder working, but still cooler and is not running as hard as it would in windows.
This would be perfect for say a LAN party, if you play classics like Quake, why get a massive thing? get this put it in your bag, and your ready to run ;)
Okay but in the end why do I suggest this? Well as I get older I have personally found I play games less and less, I look for more casual games now, mainly linux games, things I can sit down for 30mins and just play, my next PC I wont need all this power I currently have, to be fair its wasted a lot, so why spend £1000 on a gaming PC, just get a brix and throw linux on, set it up and then I can basically use the OS to browse the web and watch videos, why should I also pay for an OS to do this? I shouldnt...
So post what you think about this, would it be a good idea for you personally? Do you really need a 290X or 780Ti? or is half of its power wasted?