I use Dell almost exclusively at work. We do both AutoCAD and SolidWorks.For our R&D guys I get them Dell Precision notebooks. I have several guys happy with the M4400 and just got a couple M4600 that seem nice so far and have a better case design than the M4400 but are similar spec inside. I've been using a M4400 for about two years, though I'm not a draftsman or engineer. I do like it and it suits my needs well. Dell sticker prices are quite high, if you can order through a business with a Dell account you get much better pricing. If you go Dell, don't go with their cheapy Vostro or other home notebook lines. They are poorly built, low spec, have low res glossy screens, have greater failure/breakage rates, and in general and not great machines. Stick with a Precision preferably, or at least a Latitude if you go with Dell.
Aside from that, there are plenty of cheapy HP and other mainstream notebooks you can get in the $500-$700 range that may do what you want, but likely won't be exactly what you want or need. Figure out the specs you need and what your budget is, work from there.