Dolphin, the GameCube and Wii emulator - Forums

I don't see any issue with the G3258. I love that its cheap and if I outgrow it in a year or two... then my motherboard will support said upgrade. I went with a Zalman Copper heatsink/fan that has good ratings when used in an OC environment... Only thing I forgot was a couple of 120mm fans, but the case comes with 2 stock (with room for 2 more)...

My only concern now is the R9 280 and the 500W PSU.

You won't see any problems with the newer pentium the person who talked about them being hot and all was talking about the older pentium cpus. You should be fine with that gpu because you are using a lower power cpu and I am sure you don't plan on some massive overclock on the gpu. You can still overclock the cpu and you shouldn't have any issues.