A10-6800k comes out in June with 4.0 GHz stock clock and Turbo Clock up to 4.2 GHz, if you can wait, wait...if you can't want until June, trinity is still a good way to go.
EDIT: WHOA!!! Hang on...Auto CAD and revit are heavy duty rendering programs, you'll want more muscle than that unless you have a LOT of spare time...
Look at something like FX8350 + Discrete GPU for a solution that will do that well. You'll want the horsepower for heavy rendering like that and it will be much better for you.
AMD > Intel @ rendering/encoding, etc. it will be a much better solution for you. You'd have to go to a i7-3770k for $309 to get the same performance as the FX8350 for $189.
If you're on a tight budget, you could go with the FX6300 that would still be a good option for around ~$130 more or less that would be a better option than anything else in that price range.
You'll want minimum 8 GB of RAM in your system and 16 GB if you can swing it. Get a minimum of DDR3 1600 MHz RAM, you can go faster, but that would be the minimum speed you'd want for rendering.
Look for a good GPU too with lots of VRAM...you want something like a 2 GB HD 7870 XT or something similar to get the performance for AutoCAD and revit that won't leave you waiting FOREVER for stuff to render out.
What's your budget? For about $800-1000 depending on whether you need peripherals or not you should be able to build your system.