dragon25, in game the most Vid RAM ive seen taken is about 64Mb (could b more or less thou) so really all you need is 128 MB allocated for AH, but if you really want to improve you FR, id suggest just getting a Vid card. This not only frees up your RAM but it also takes a load off the processor.
I have a AMD Athalon 2000+ (1.66 Ghz) with 1Gb of ram and a 128 MB nVidia GFx 5200 and it runs AH @ 1280x1024, 1024 Textures w/ hires updates, and all visualizations except object detail @ 100% @ 30-40 FPS
The computer i am on now is a AMD Semperon 3300+ (2.207Ghz) NVIDIA GeForce4 MX Integrated GPU 32MB allocated (havnt had AH go above 32MB on this comp yet usually sits around 23 Mb) 352MB ram (128MB 166Mhz, 256MB 266Mhz) and i can only run AH at 1024x768, 128MB textures, object detail 50% and I only get 15-30 FPS
This is when my Vid memory clock is at 267Mhz (norm) i get 15-30 FPS, when i clock it at 680Mhz i usually get 18-35 FPS, so far the highest ive clocked it is 1.01Ghz and it usually sits at 20-40 FPS.
BTW i am kinda new to overclocking, all this has done to my comp is raise the temp from bout 25-27C (dont ask for F from me IDK F) to 28-30C while not gaming, while gaming the temp raises from 30-34C not OC'd and 32-37C OC'd (HWDoctor chip is built onto my motherboard, tells all the V's, [eg. Vcore, , VTT, +3.3V, ect.] CPU fan RPM, CPU temp)