I don't know what happened in the file, but the render quality is simply a matter of you learning lighting and how to use the renderer. It has a lot of options. You may have to also tweak the textures. Lots of power in the shader room. The lighting does need some rework. Did you use transposer? Are you on a mac or PC? Make sure you remove unused master shader and objects. If you brought things in multiple times you may have trash that needs removal. Usually, the quality of the textures effect the render greatly tho and I don't know what textures you are using, but poser procedurals are not going to look the same in carrara. Learning how the lighting works is key. Probably should turn off you ambient lighting also. It starts at 20% so turn it to 0. Some lighting and special effects and even texture effects can quickly add to render time. Depends on what they were. Did you see what happened to you ram usage when you tried to do this?

No need to think outside the box....
    Just make it invisible.