Is it worth to upgrade my computer or should I custom-build a new one?

PakOne

Honorable
Nov 18, 2013
210
1
10,685
I want it for gaming.

One year ago I bought a pre-built desktop computer with these specs:

Intel Core i3-3220 (3.30 GHz)
8 GB of RAM
NVIDIA GeForce GT 620 (OEM)
300W Power supply
Windows 8

I wonder if it's worth to upgrade my computer's video card and power supply to an AMD R9 280 and a 500W power supply or if I should custom-build a new computer with more or less these specs:

AMD Athlon X4 860K (3.7 GHz)
8 GB of RAM
AMD R9 280
500W Power supply
Windows 7 or 8.1