Are you planning on reusing anything from your current machine like the mouse, keyboard, hard drives etc..?
I should be able to spec you out something for under 2 grand. I'm guessing you'll need an i7 for your CAD stuff..?
Edit: Forget about a small form PC. Get yourself a full tower EATX case. It's going to be huge but will have GREAT airflow and a shitload of fans in it to keep everything as cool as a cucumber.
Another Edit: How about this: http://uk.pcpartpicker.com/list/R99F8K
I haven't added any storage, optical drive, keyboard or mouse because I've assumed that you'll be reusing the ones from your current machine. This basically the machine I built in November, except back then I didn't have a GTX 1080 because they weren't released at that time.
I've also added another 3 fans to the case which cost me around a fiver each from eBay and another 16GB of DDR4 because it was on sale for around £36...that's around half the price I paid for the first 16GB in my original build.
That PSU may seem like overkill but will allow you to add another 1080 in HB SLI if you fancy it later on down the line.