('installed', '/', 'x11-base/xorg-server-1.5.3-r5', 'nomerge') pulled in by <x11-base/xorg-server-1.5.99 required by ('installed', '/', 'x11-drivers/nvidia-drivers-173.14.18', 'nomerge') Can you provide any evidence for this blocker? As far as I know current Ubuntu users can use this driver with xorg-server 1.6.0.
Looks like a dup of http://bugs.gentoo.org/show_bug.cgi?id=258499
fixed.