The crazy, speaking of poly counts I dont see why there should be a problem with having 10-20 of those 2000k guys running around, actually more so with the level detail you're using. My current project's skysphere alone is 2000 polies, not to mention a 20k map with a 4096x4096 texture, thats excluding other player object's, lag from online play, special visual/sound effects, and all of the collision checks, and Im still clocking around 50-75 FPS on my relatively old computer. Im fairly sure you could spend 30k polies on the baddies if you leave your maps as low-poly as they are right now, but up the texture quality a bit.
Eitherway goodluck.
