Yeah, you don't have much options here at the $700 range. In fact, the video card alone will be your biggest set back.
Typically dedicated mobile video cards that are designed for CAD (usually its just the drivers that makes all the difference) are far more expensive than the CPU and worse, are anywhere from 10-25% worse performing than their respective PC counterparts.
If your able to use a gaming video card to perform your CAD work, then I highly recommend you upping your budget and get into some gaming laptops such as the ASUS G lines. At the very least they are usually installed with a nVidia 560 or better and a i7 CPU.
To switch between tasks easier, that'll be up to you to afford buying a SSD of any kind. But that adds on to the price as well.
Otherwise my suggestion would be this:
Dell Precision Mobile Workstations - Performance on the Go | Dell
It ain't the fastest, but its the closes to your price range if you are willing to pay the $150 to upgrade to the Quadro 1000 (which sadly equivalent to a nVidia 540m video card).