Opinion regarding my AMD based gaming rig.

I would go for a 250GB over the 120GB SSD - it'll be more cost effective per GB and you'll thank yourself over and over that you afforded yourslef the additional space, especially since you aren't including a regular hard drive

How are you cooling the CPU?

I agree with you on the PSU, a good 650W will be enough, Seasonic, Antec HCG 620W or the XFX TS or Core 650W

Also, is there any way you can stretch to the FX 8320? The newer Vishera chips are better overall performers.

I personally prefer air cooling. You only get about 10 degrees more at the most over the best air coolers. And I prefer not to have liquid in my computer. If you are planning on running crossfire or SLI in the future? If so, then you will want to stick with the 750. If not, then the 650 would be more than enough.

Now the CPU you have listed is an outdated processor. I would go with the AMD FX-8320 or the 8350. Otherwise, everything else in your build looks pretty good. If you want, you could give me a budget and I could try and come up with another option for you.

Edit: snowctrl is right, you should either get a bigger solid state or get an additional hard drive.

If your CPU is overclocked and you also overclock the GPU, 650 will only be adequate. Both the CPU and GPU can pull close to 300 watts each in that scenario. Also, stronger power supplies from good companies will give smoother power delivery. Don't skimp on the PSU.

My opinion:
I like:
Seasonic is excellent, and you are right, a 650w unit will be sufficient for any single gpu card you want.
I have no problem overprovisioning a PSU a bit. Say 20%.
It will run cooler, quieter, and more efficiently in the middle third of it's range.
A PSU will only use the wattage demanded of it, regardless of it's max capability.

Ram is good, assuming it is a 2 x 4gb kit.

Love the Samsung EVO. Can you manage 240gb?

Case is good.

Not so certain about the real guts of your gaming build.

On the cpu side, you might read this article in it's entirety.
I do not agree with their validity of value, performance per dollar part.
To my mind, it should be that given a dollar budget, what is the best I can do now and perhaps allow for a future upgrade.
http://www.hardwarepal.com/best-cpu-gaming-9-processors-8-games-tested/
I estimate your budget for combined cpu and motherboard to be $300 or so.
I would use a $90 Z97 based motherboard like this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157529
and a intel quad of some sort. Perhaps a $200 i5-4690
http://www.newegg.com/Product/Product.aspx?Item=N82E16819116991

The main engine of good gaming is the graphics card. A R9-280X has excellent benchmarks, on a par with a GTX770.
but, I see many unhappy R9 users on newegg for your card. 25% 0 or 1 egg.
Compare that to the most popular GTX770 that is equally priced with 7% negative rating:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130921

As to liquid cooling:
My canned rant on liquid cooling:
------------------------start of rant-------------------
You buy a liquid cooler to be able to extract an extra multiplier or two out of your OC.
How much do you really need?
I do not much like all in one liquid coolers when a good air cooler like a Noctua NH-D14 or phanteks can do the job just as well.
A liquid cooler will be expensive, noisy, less reliable, and will not cool any better
in a well ventilated case.
Liquid cooling is really air cooling, it just puts the heat exchange in a different place.
The orientation of the radiator will cause a problem.
If you orient it to take in cool air from the outside, you will cool the cpu better, but the hot air then circulates inside the case heating up the graphics card and motherboard.
If you orient it to exhaust(which I think is better) , then your cpu cooling will be less effective because it uses pre heated case air.
And... I have read too many tales of woe when a liquid cooler leaks.
google "H100 leak"
-----------------------end of rant--------------------------

I suggest a noctua nh-D14 or phanteks with dual 140mm fans.
Your pc will be quieter, more reliable, and will be cooled equally well
If you use a non "K" intel cpu, it will run cool enough at stock. I might use a $30 cm hyper 212 regardless because it will be quieter.