ATI cards by default only switch to higher RPM at one very late point, meaning that from 0 to 70C, you run 33% RPM, and then all of a sudden it jumps to higher RPM. You have to wonder why at this stage, and I can only say that if ATI ships the card like this, and adds a warantee on top of that then you shouldn't worry too much - untill your warantee falls away and by this time chances are that you already upgraded again.
Just check your temps with Ati Tool and ATi Tray Tools. MAYBE you have a cool system and your card is okay. If the temps are a bit high (from 85C to 90C up in my view) then you might want to adjust your fan speeds to toggle at lower temps, at the cost of noise though.
Grab another 512 stick. While a cpu will probably give you an overall faster system, doubling your memory is really cheap, and you'll notice a much smoother system. Just make sure you try and find the exact same memory as the 512 you currently have. Some motherboards don't like it when you mix and match different brands. Above all that though, a score close to 10k in 3dmark 05 is right where it should be with a videocard like that.