Hello, and thanks all for the replies. I'm sorry for the delay in replying
It seems OCing my CPU isnt really feasible at the moment, as even using the autoclock function in AMD Overdrive leads to a crash around the 2.9ghz mark. That coupled with bios that cant be unlocked (apparently) mean that it doesn't seem like a possible option at this point. I assume the crash is due to the motherboard's limitations though I've nothing to confirm my suspicion.
Regarding the PSU, I'm not sure of the exact make now. I recieved it from a friend awhile back, and I was told its in the 700 watt range. This was a huge upgrade from my default 300-ish watt model that came with the PC.
Duly noted on the card issue. I'll do what I can to upgrade the CPU in the future, and the GPU will be on the list afterwards.
Thank you for the advice everyone, its certainly appreciated. ArmA2 was one of the games I was hoping to handle with this PC setup, and I regret having not done any more research beforehand.