According to Nvidia's website their most powerful laptop GPU is their
GTX 280m. The specs show it has 1GB of VRAM. The OEM could have potentially added extra memory but it would yield little benefit.
A comparison between the mobile GTX 280, the real GTX 280, and the real top of the line GPU the GTX 295...
GPU GTX280m GTX 280 GTX 295
Processor Cores 128 240 480
Texture Fill Rate 38 48.2 92.2
You can compare the rest of the specs yourself at
http://www.nvidia.com/object/product_geforce_gtx_280m_us.htmlhttp://www.nvidia.com/object/product_geforce_gtx_280_us.htmlhttp://www.nvidia.com/object/product_geforce_gtx_295_us.htmlI have only once seen a company use regular GPUs (not mobile versions) in laptops and that was with Falcon NW. Either way, the extra performance of a high end GPU in a laptop eats away at battery life and generates an excessive amount of heat.
The best system you could put together right now (if money was no problem) would probably use 3x GTX 285's in SLI. Few can justify that kind of expense. Even a single GTX 295 can run any game on the market exceedingly well.