Z-Buffer

If I am using the Z-Buffer in OpenGL, there are a few things I would like to ask about it. My engine is using quake 2 models and a bsp for the world geometry. The BSP works fine and I don''t need a Z-Buffer to render the world. But the problem comes when I want to render the model. Thats why I think I might want to use the Z-Buffer to draw it. My first question would be, is there any way I can get around using the Z-Buffer because I don''t want to rely on things like that. I want to have all that sort of stuff handled by me (don''t ask why, I just do My second question is, it would be faster to draw my world geometry in front to back order would it not? There are a few reasons why I think this. The first would be that if its done in front to back, there would be less assignments to the z-buffer. This will hopefully provide faster testing and would still enable me to sort my stuff. Any other ideas would be appreciated. Thanks Shawn