STALKER is fixed, mid range system, its jaggy but SCARY.
And $$$ cheap. Free compilation of mods in one:
http://www.moddb.com/mods/call-of-pripyat-complete
Thank you, i just spent my first few hours safely (not getting shot at) on your server setting up my controls, losing items in the backpack and almost dying from zombies!!! Perfect. Now on to figuring out my video settings yay!!!