What laptop should I buy for dual-monitor & photoshop/lightroom?

I'm looking to buy a laptop, but I'm concerned about the ability of it to handle such software as photoshop and lightroom - additionally dual-monitor use - at the same time in pretty good screen resolution size. I'm wanting to be able to edit photos on the spot and give to client moments after taking the pictures. What are the minimum hardware requirements I should look for that will be able to handle this demand? Will I need a non-mobo-based video card to handle dual monitors and higher screen res?|||I think u should get an HP cuz my laptop hasnt had any problems