I am trying to help my brother purchase a laptop for use with work...hence he needs a laptop because he travels. He was hoping to spend between 5 and 6 hundred on one. I am pretty knowledgeable about computers, but i just dont know how a graphics card is going to come into play or effect CAD. He is wanting to use some 3D modeling...I think. What kind of card should he have? Is there a huge difference between these cards when using CAD(besides the high end cards...hes on a budget). Is it worth spending a little bit more for say a new moderately priced card? Anyone out there have any suggestions or comments?

It depends on the specific CAD application and on the size of CAD data, but having a good 3D accelerator (graphics card) can make a huge difference in the performance of your CAD software.
 
There is a separate class of laptops - mobile workstations - which are tuned for 3D CAD applications (see e.g. HP). But any strong notebook with an integrated nVidia or ATI accelerator will do as well (for limited budgets).

thanks for the post

Dell all the way.  You can get in trouble if you build your own.  Plus as you upgrade to new software the Dell machines are more capable of running Alias Studio or maya or MAX