Many objects on screen

I am currenty setting up a scene that has upwards of 5000 buildings and 2000 dts objects in it and I am hitting some serious slow downs. Obviously this is a lot to be on screen depending on the geometry. I have a problem though. I can turn the geometry down to about 4 polys and put around 1000 dts objects on screen and still get massive slow downs. I know it cant be the geomerty as that is only about 4000 polygons. Does TSE have a problem displaying tons of objects? I also cant really put in more than 1000 dts objects or the game crashes. Any ideas on that? I want to use the terrain and create a huge 32km block of terrain with many buildings and trash around but i cant if i get horrible frame rates.

Just trying to look for an idea of what might be causing this.

Thanks