The Mobile Core 2 Extreme based on the Santa Rosa core is the best processor and currently the most powerful GPU combo is dual 7950GTX cards in SLI. That combo is hard to find though. Look at this.
http://www.newegg.com/Product/Produc...82E16834220210
You might want to custom configure a laptop at ABS which will use quality third party parts. You have the option of the GeForce 7950GTX or the 8700GT.
http://www.abs.com/app/config.asp?mono=1994
http://www.abs.com/app/config.asp?mono=1957
At this point it is unclear of which single GPU will come out on top but it looks to me like the newest games at lower resolutions and AA settings will favor the 8700GT while older games at higher resolutions and AA settings will favor the 7950GTX.
With the Dell you mentioned above you are stuck with an nVidia Quadro which isn't the best for gaming.