GTX 970 VS Radeon R9 390 8GB

this is a good thread to look at. bluescreen has some builds for various price ranges in this thread
http://www.beamng.com/threads/computer-building-guide.12416/

 

I have a feeling it lacks case fans, but it's great otherwise. Or can you just use your old fans for it?
EDIT: My bad, it has some fans, you can buy some more if you want more airflow later on (actually, that could be good for your GPU, since you have the Radeon).
I can recommend the Arctic F12 PWM and F14 PWM. Quite cheap and pretty performant.

 

390. efficiency be damned.

 

I have no clue what case fans do or go... please explain

 

See my post edit. Case fans are cooling fans that you put on your case to improve airflow. Your case comes with two and can hold quite a few more. I think you should just try the configuration out without any extra fans at first and check your hardware's temps. You can check that with programs like Piriform Speccy. If the temps are quite high (like... 45-55°C and more?), you should probably add some more fans.
Any more questions? Have I even AWNSERED your question properly?

 

Yes you have! Alright, Whats a good temperature for the PC to idle at?

AND: Is this a good combo:http://www.ncixus.com/products/?sku=103071&vpn=SGB-3012-KKMF1-US&manufacture=COOLERMASTER

 

20-30C is good for idle. Up to 40C is fine. Load temperatures are what really matters - anything below 70C load is fine, 70-80C is a bit too hot, anything above 80 is bad for the CPU.

Also. Heard good things about that m/k combo. Keyboard is rubberdome so meh, it's mech or nothing for me. But for $30 kb+m it's pretty good. Don't expect anything high end though.
--- Post updated ---

Read part 6 of my computer building guide. Explains what fans do, where they go, different types, and why airflow is important.

 

I have an old Cherry rubberdome. It has a very good quality and I really thought it was mech before I opened it. You just can't throw it in one bucket with those ugly keyboard-like things that they have on schools.
What I'm saying is: If a keyboard looks like a mech but is rubberdome, it's still very very good.