Word of advice when buying a gaming machine is to buy a gaming machine or one with the best possible CPU GPU CPU-cooler and power supply upgrading the Hard-drive and Ram can be done cheaply.
Trying to cut corners by buying a home or business PC for gaming and throwing in the upgrades may seem cheaper at first but its a headache and the saving isn't much since your forced to hunt around for low profile CPU cooler fans and small form graphics cards.
If you have a home/business micro ATX cases and want a better or high end GPU your looking at
MSI HD 7850 OC 2048MB
ZOTAC brands
Asus GeForce GTX 670 Mini 2048MB which should fits into a ITX mini form factor as well.
I hope these words of wisdom help
Trying to cut corners by buying a home or business PC for gaming and throwing in the upgrades may seem cheaper at first but its a headache and the saving isn't much since your forced to hunt around for low profile CPU cooler fans and small form graphics cards.
If you have a home/business micro ATX cases and want a better or high end GPU your looking at
MSI HD 7850 OC 2048MB
ZOTAC brands
Asus GeForce GTX 670 Mini 2048MB which should fits into a ITX mini form factor as well.
I hope these words of wisdom help