I work for an engineering firm. We use several different AutoCAD programs including AutoCAD, Microstation, and Maya. If you are building a workstation dedicated to CAD design, you are going to want to stick with a professional graphics card. Gaming cards do not have certified drivers to work with the major CAD applications.
It sounds like what you are doing is mainly simple 2D drawings, not much 3D rendering. If this is the case, go with a low end professional card. With your budget, I would go with the AMD Firepro V4900. That is what we use in our lower end workstations. The next step up from that would be the V5800 or W5000, but I don't think your budget will allow for that. Professional graphics are no doubt more expensive for the hardware you get.
In that price range, you will not find a laptop with professional graphics.
If you are partial to NVIDIA, go with something from the Quadro lineup, however, they do not have anything comparable to the V4900(In price or performance).
Be sure to pair it with at least 8GB of RAM and at least an i5 processor.