Should I get more RAM or a better processor?

your system spec is way over the minimum for this game. the only weak point i can see is the 9440; not really a gaming card. maybe you are expecting too much for high settings. you are going to upgrade sometime, so why not spend the cash on a decent gfx card; you can always migrate it to a new system down the road! don't know what you have to pay in AUS though...:-)