Synergistic research Rel spec cable

What is the best Synergistic research Rel spec cable? Im currently using the stock cable in my Rel B2 subwoofer. I think there are 4 rel spec cables. Which cable will suit my Rel B2 best? My speaker is Harbeth Compact 7 es-3 and Accuphase integrated amp E-350.
The best Synergistic Research Rel spec cable is the Tesla Rel Spec Reference Active. I use the one step down cable because it is very flexible. It's called the Tesla Rel Spec 2. The reference cable is a little too thick and harder to bend in my system. Both are excellent and well worth it. The Cable Company can set you up with a demo if you like and you can compare the two cables.