GTS 450 GC Maximum stable OC?

So, I picked up the Galaxy GTS 450 GC several months ago, and it's been a pretty solid card. Sure it's not top tier GPU status, but it's gotten me through. I am also using a AMD Phenom II X6 1045t CPU with it.

Anyways, I have recently gotten into Arma 2 and Day Z, which...to say the least, are not optimized well. In Day Z, my framerate varies from 18 in city, to 50-55 outside of towns.

In Arma 2 however, I mostly get 40+ no matter where I am.

My question is this: If I overclock this card, would it even be a noticable difference in framerate? If so, I would be interested in knowing what I can OC to stable, and with what software is best for testing. I've been using Afterburner for quite some time to monitor my temps and control fan speed, so I am aware of how easy it is to overclock. I tried a couple of months ago, but ended up freezing up my computer and after that, I just set it back to stock speeds.

Anyways, have any of you overclocked the card? If so, what was the highest stable you had without adjusting voltage?

:Edit: I should add that Arma 2 is not the only game I play, of course. I play as many games as often as I can. Arma 2's poor framerate is just what got me in the mood to look into overclocking. This would be a general purpose OC.