Tiny,
I suppose this already have been discussed before, but... what about using two sets of 3D models?. I mean... if you have a high-end machine/hardware/gfxcard, then what's the reason for not seeing more complex and detailed models?. In the configuration options, you could choose a detail option based on the power of your PC.
In addition of this, I can tell you that I've been working with 3D modeling systems for a long time, and there are some tweaking methods for optimizing the 3D meshes in order to save a lot of extra polygons, and without sacrifying the model appearance.
It's only an idea
