Memory doesnt help FPS.
I just upgraded from 512 to a full gig for exactly that reason and it did nada for my framrates.
Also upgraded from a Vid card with 128 memory to 256 with the same results with the exeption of I can run animated water but dont because I find it too distracting
It was explained to me that memory usually wont help your FPS as AH is CPU intencive and not memory or graphics card intencive.
I've found the best way to improve FPS is through the sliders which I sometimes adjust on a nightly basis depending on what Im doing. And how the game is performing that particular night
I'll set it one way if Im GVing, another way if Im furballing.
also I find some of (but not all) of the aftermarket sounds can effect game performance
Another thing you can do, and should be doing anyway.
Is open your case and check for dust. you would be amazed how much dust gets inside these things even after only a month or two.
Recently discovered when dusting its best to remove the fan from the heatsink on the CPU as dust builds up there and doesnt get blown out easily if at all with it on.
Almost roasted my CPU because of this.
Dust causes the system to retain and buid up heat which will in turn degrade system performance.
And lastly, whenever a new version of AH comes out I manually uninstall AH then reinstall it fresh.
By Manually, I mean instead of using the "uninstall" utility. Go into windows and find the AH files and manually delete them.
I find doing it this way eliminates the stutters and sometimes the VOX related freezes that some folks report. And simply using the uninstall utility does nothing.
Anyway, these are the things that work for me.
Hope they help
The best "Bang for thre buck" for AH seems to be the CPU which is what Im planning on doing in the very near future.