There is an alternative option for your laptop.
There is a way to use ExpressCard ports, DisplayPort, Thunderbolt ports and to a lesser extent replacing the wifi with trickery to hook up an external GPU powered by an external PSU. Not exactly portable but can be used as part of a docking station type set-up at home.
Take your laptop out with a passable GPU if you really must play on the go, then hook it up when you get home for much, much better performance.
The only problem is the various hook-ups run at different speeds, for example ExpressCard runs at around 1.2x PCIe, instead of the 16x your desktop enjoys. This can result in a chunky hit to performance, 50% or so. However even with such a hit it a 560ti at 50% or something still runs much better then most laptop GPU's.