the model polycount depends on the quality you wan't to achieve... Unreal monsters have about 8000 polygons and gs models are some about 1000 polys... Fuxerz might make 4000 poly model and I might make a 3000 poly model... its up to you man!

The more polys, the better comp you need... but Id go for 1000 polys for little enemys and 3000 for big ones...