I've seen videos and screen shots that people have made with superb graphics for AHII. I've also heard some people are getting over 100 FR's with all hi-res graphics.
Currently I have an nvidia GeForce 8600 GTS, and can play on Hi-res graphics with roughly 60-100 FR's. I also can turn on detailed terrain, water, and local reflections on water and still get 40-80 FR's. However, when I try to turn on bumps on terrain, self shadow, and smooth self shadow I drop down to 20-40 FR's and I get a lot of screen freezing (lasting anywhere from 1-10 seconds, and sometimes a host connetion lost). With the 8600 GTS Vid Card I get 512 MB's of memory and with all of that stuff turned off I only use about 80 MB's of memory, and even with it turned on I only use 120 MB's max.
I know some stuff when it computers, but I'm nowhere close to being a "Computer Nerd" (or "Computer Wiz" as you would probably call it

), so my question is why would my computer struggle with bump terrain and self shadowing but run great when I turn them off? Are Video Memory and Frame Rates two different things? I only use 120 MB max out of 512, yet only get 20 FR's and screen freezing.
Am I just missing something, or should I just go ahead and get a new, better video card?