Here is a pic of my x1900gt next to my old x1600xt.  Man its huge...a full 9".  I ordered up some forged copper Swiftech ram sinks and a mammoth Thermalright vga sink for it.  I thought I would post my OC' ventures for you all.  Its for my PC workstation, but the same principles all apply to the mac card.  Stuff should be here on Weds and Ill go from there.

By the way with stock cooling I have the gpu @ 625 (same as xt model) and memory@1440.