Hi C,
Is this screenshot from the 13k one or the 6 k one,it looks good , but you have waaaaaayyyyy too many wasted poly's everywhere.
Try to optimize your mesh as far as possible,cylinders,especially those on the rear of the tank do not need to be nearly as high poly as this render suggests.
Also , spending poly's on the reactive armour on the front etc,can simply be done by texturing alone and need not be actualy geometry.
When I get home,I'm currently on vacation , I'll upload a challenger tank I did for a BF 2 mod,its strenght is the fact that is only 2500 poly's and very light in geometry.
The model is very nice though.