Take a look into the HP EliteBook laptops. These things are highly customizable and offer as much horsepower as you can ever want really. We have sold dozens of these performance laptops and I own one myself, they really are rock solid computers and you can do a ton with them.
I know that the Ivy Bridge version of the new 8X70W workstation EliteBooks will be releasing soon from HP, but even the Sandy Bridge workstation systems just are phenomenal computers.
I agree with choucove.
The ellite books are everthing made for business computing and highly customisable.
Most business users who have this have given it a good rating on design stability and portabillity and power.