Something like this would do fine:
CPU: i7 3930K
CPU cooler: Scythe Mugen 3
$49.99 ( or something similar )
Mobo: Asus Sabretooth X79
Memory: Gskill RipjawZ 8x4GB 1.5V CAS9 1866Mhz
GPU: Gigabyte GTX580 3GB
Optical: Asus 12x BD-R
SSD: Samsung 830 256GB
HDD: 2x WD Black 1.5TB
Case: Antec P280
PSU: Seasonic Platinum-1000 1000W 80+Platinum
Total: Pretty much $3000 even.
If the 3D design is just a hobby for you, a 1155 based i7 2600k build will work better for you and let you get more gaming juice.
But here is one way to spend 3k USD on a computer that should be great for both gaming and the 3D modeling.
Basically changing the CPU and Mobo and using the saved money to another GTX580 would make the more gaming oriented build.