Take a look at the Monster here: Tweakers Page - What kind of PC to use? and exchange the E5-2687W (2x) for the newer E5-2697 v2 (2x). Possibly exchange the GTX 770 for the GTX 780 Ti.
It will NOT be the World's Best, that would require 4 x 15-core E7-4890 v2 CPU's, 512 GB memory, 12G SAS etc. but at a different price. Around $ 200 K.
Thunderbolt is only available right now on Desktop or Mobile platforms in general on the PC side. You can get the HP Z820 for their add on card but the price range gets extremely high. At some point you will see the Thunderbolt controller cards out for open/cross platform but not yet.
The Asus Z9PE-D8 WS is the board you want if you go dual xeon along with the 2690V2's or the 2697 V2's. 128GB of ram with 8x 16GB reg dims and the Titan Black Edition if your using Premiere, AME, Speedgrade, or Davinci. The storage setup is the real question. SSD for the OS is what you want obviously. However the Media volume will depend on your plans. For example a SSD raid with 5x Crucial M550 drives with an Areca ARC 1883i 12Gbs controller is enough for 4K DPX files if you need to use up to those in your workflow. That volume size is normally more than enough for major compositing but may not be enough for editing workflows. That is where the larger 8 or 16 Bay SAS arrays with a storage unit come into play. However it takes the 16 Bay SAS storage units to handle up to 4K DPX files with mechanical storage.