For CAD work, the FX-8150 is a little better than the i5-3470.http://hothardware.com/Reviews/Intel-Core-i53470-QuadCore-CPU-Review/?page=4
As for prices, the i5-3470 is $190 at Newegg. You might as well get a $200 FX-8350 - it's a little better than the FX-8150. Newegg is out of the FX-8150. Good motherboards are typically available for around $100 for either CPU, it depends on the features you want.