Personally, it's not "brick intensive" that borks up my computer. It's "face intensive". The more rendering faces that I have to see, the more CPU-intensive it is. Specifically, it's things like lips on the ends of ramps, the side edges of ramps, and basically every single Omni Quad that lags me. That AND pointless hollow interior spaces. Those increase my rendering facecount too. I've found that I actually lag LESS if I use MORE bricks to "fill in" all unused empty spaces.