Looking for 300$ Build for Gaming Specs

Hi, I'm new to the forums and also it'll be my first time building a budget rig (around 300$). I'm a bit meticulous on my build cause I'll be buying a lot of units for my internet shop, so I was hoping it will be a bang for my buck. I don't wanna end up regretting on the units I'd bought knowing that there's a better one at a lower price.

I know there's a lot of experts on these forums and I'm considering & hearing all opinions. Before I was here I've ask a lot of my friends for their opinions already and I'm bringing it to another level (yes this is another level, cause I've learned a lot of insights just by reading on this forum).

The rig I wanted should fit the following criteria I've set (and who doesn't want either)?
1. Price to performance ratio (For the whole build or for each individual part)
2. Durability (CPU would be subjected to a lot of use, really. I'm planning for parts that would be good to last for 3-4 years before I'll buy a new one. Easy maintenance also would be a great perk)
3. Upgrade ability (When never games comes out, cpu has still a lot of room for it to be upgraded to run those games)
4. Low Energy Consumption (performance to watt)

So far I've build my own rig. Any suggestions are welcomed. You could post your own build too and point our the perks over mine . I live in Asia though so I couldn't put up the price equivalent. And also 2013 hardwares is not yet ship in our country so preferably I could only use 2012 parts.


AMD BUILD
Build#1
CPU: AMD APU series: a6 5400k -
RAM: Crucial Ballistix Elite(4GBX2) PC1866DDR3
VC: Built-in
Motherboard: Gigabyte GA-F2A55M-DS2 -
HDD: Western Digital 500GB SATA Blue -
PSU: Corsair VS450 450 Watts -
Case: Any Mid Tower ITX Case around 20$

Build#2
CPU: AMD APU series: a8 6400k -
RAM: Crucial Ballistix Elite(1GBX2) PC1866DDR3
(rest parts is same as above)

INTEL BUILD
Build#1
CPU: Intel Pentium G2020 ivy Bridge 2.9GHz -
RAM: 4GB DDR3-1333 Corsair -
GPU: SAPPHIRE Radeon HD 6670 -
Motherboard: Gigabyte GA-H61M-DS2-B3 -
(rest parts is same as above)

I'm hearing good reviews w/ WD HDD and Corsair so I might be inclined to buy those.

Hopefully your suggestions would be an eye opener to finalize what PC i should be buying. Thank you ahead guys!