I want to build a system with 8 CPU cores

I want to build a custom system with 8 or more CPU cores.  Is this possible with any Intel or AMD (or any other "x86-compatible" company) chips?  What about motherboards that support this?

I need to build such a computer that'll take care of intensive rendering sessions for my graphics work, and my desktop computer I use is underpowered for anything other than Preview-quality renders.

I don't think you can get an off the shelf motherboard that'll support all those cores.  you're better off building a distributed network