I also have a Noctua paradise! I have 2 AF-14 iPPC 2000 PWM and 6 NF-F12 iPPC 2000 PWM. All amazing fans. I like your build, it's quite simple yet powerful!
OMG I took apart my GPU block the other day to do some cleaning that it didn't need and I spent 20 minutes trying to get the gasket in place, I almost ripped my hair out in frustration.
That fluid is not good for home systems that are going to be used for extended periods of time. It's only for showing systems off and photography.
http://www.mayhems.co.uk/mayhems/index.php/guides/mayhems-aurora-guide
The term silicon lottery does not apply to PSUs. It usually applies to overclocking CPU or GPUs which have a silicon die. The idiom or term you're looking for is luck of the draw, because you never know when you'll get a bad unit.
Welcome to the forums. Just be aware that this forum can get toxic at times. If you see a thread about politics or AMD vs Intel, it's in your best interest to avoid those to keep your sanity. Gloom and doom aside, enjoy your stay!
For the love of your wallet, do not get a GTX 960 or any card for that matter as a dedicated PhysX card. Your 980Ti can already do that. To answer your question, it's not worth it IMO.
Download and run Display Driver Uninstaller on your current HD 6850 system.
Once you run this software, remove your HD 6850 and install your GTX 950
Download and install latest GeForce Drivers
Done!