Dell Precision T5600 Intel Xeon 2TB Workstation

This is the real deal! Ditch the processors with 2x E5 2687W or the E5 2690s. This upgrade would have costs you around 300-400USD per pair processor used retail C2 stepping processor. You will get 16 core 32 threads. The current Quadro probably is the lowest end around so you may want to swap that out also. You can get 8×8GB RAM ECC for under 200USD. A powerhouse for under 1000.

If you want more connectivity, get the HP Z620 woth options to add Thunderbolt 2 card. Unfortunately not available for this Dell.