Replace Velodyne HGS-18s with Revel B-15s?

I placed an order today for the Revel Ultima system (Studios, Voice w/pedestal and Embraces). Though I used matched Velodyne HGS-18s in my soon departing system, I am considering replacing them with two of the much more flexible B-15s. I am very interested in the thoughts of others regarding this alternative.

Thank you.
I have the Ultima system with studios, voice, and embraces. They are wonderful. The timbre matching between everything is seamless. I had a Velodyne HGS12 (not comparable to the -18) and bought the ultima LE-1 + 2 subs. Its beyond my expectations. On well recorded live albums, e.g. Bonnie Raitt Road Tested DTS, you are there, absolutely no difference from a live concert. You've gone this far, you might as well make it perfect.
In the meantime try putting those Velodynes on 6 inch stands. Even if you just make a box for them it will make a huge diffrence. It cleans the bass up quite a bit.
I just went from Velodyne subs to the B-15. Your going to be amazed at the difference. They are tighter, blend better with your speakers, faster, more musical and have more slam. You will be very very happy with the switch. Ask your dealer to let you bring one home and A/B with one of you HGS's. Good luck and Happy listening.