I don't use it for 3D modeling, but that is what this series is designed for. The battery won't last and you are hauling around the brick for the power cord, but mine does accept a ton of RAM has two hard drive slots, a dvd drive and many other ports.

http://www.dell.com/us/business/p/precision-laptops.aspx?c=us&cs=04&l=en&s=bsd&~ck=mn

Dell overprices their RAM so I would order something with minimal RAM and upgrade with RAM from Amazon or Newegg.

There may be newer technology from competitors like Lenovo and HP, I am just familiar with Dell's mobile workstation.