It is likely that any motherboard will work fine, because CAD might be more limited by the GPU. Many CAD programs are somewhat intentionally limited on "consumer" graphics cards, and needs high-end Quadro or FireGL cards to do nice things like anti-aliased lines.
I'd spend maybe $500 on the mobo + CPU + PSU + RAM, and another $500 on the graphics card. Try to get the best graphics card that you can afford on the "recommended cards list" for your CAD software. And sometimes, those lists are not updated often enough, so they'll recommend old cards, where the newer, updated version of the card is usually better for less money, so consider that too :-/