Videoguys recommend Quadro Mobile GPUs
The Adobe Mercury Playback Engine in Premiere Pro CS5.x is amazing. When you combine it with a mobile Quadro card you will be able to edit multiple layers of assorted HD footage foramts in real-time. Avid wants a Quadro card for Media Composer as well.  We really like the new Quadro 3000M with 2GB of GDDR5 memory and 193 CUDA cores!

The NVIDIA® Quadro® Mobile Workstation product family is a complete top-to-bottom range of solutions with unmatched performance and quality for the most demanding professionals on the go. From digital content creators on a movie set, to design engineers at a remote plant, to geo-scientists on an oil rig, Quadro mobile graphics processing units (GPUs) are the trusted solution for professional 3D applications.

The newest NVIDIA® Quadro® mobile professional graphics solutions are true technological breakthroughs, featuring up to 4 GB of graphics memory and 384 CUDA cores. Built on the innovative NVIDIA Fermi architecture, the latest Quadro mobile graphics offerings integrate high performance computing capabilities with advanced visualization, transforming your new laptop into a mobile super computer.

Click here to learn more about Quadro Mobile GPUs and for a great cross reference list of HP and Dell laptops that can be configured with them.