If you can wait, I'd get the i7 Core mobile CPU laptops coming out later half of this year. The multi-threading almost halves your rendering times. Worth the wait I'd say.
If not I recommend http://www.pcspecialist.co.uk you can build one with 512MB Nvidia 9600M GT graphics card for under £1000 pounds. I have one and the diffault setting makes sketchup lines look super SMOOTH! without anti-aliasing turned on! Incredable for presentations n walkthroughs.
I'd be honest with you PCSpecialist are not really the best quality as mine broke under a year (arguably not their fault as my GPU, the 8600M GT died and if you read internet forums this card is dying at a dispropotionate rate on all manufacturers laptops including Apple) but their service is incredable. They didn't ask any questions had it sent back and upgraded my chasis (Old Chasis had a 8600M GT which died) with new GPU all for free! Sent back to me in a week. So basically I got a free upgrade from them.
The 9600M GT gives amazing default display quality.