Well I own a Rel B3 and just helped install a S9. Personally I think the B series is a lot better. My B3 digs deeper with better attack and decay (just replace the stock aluminum cable - the S comes with a copper cable). The B1 is even better as far as going low. The downside to the B series is if the amp goes it's gone. Sumiko/Rel has no parts. Mine is just turning 10 years old and I don't power it off. Once about 2 years ago the sub wasn't working but yet the led was on. Turned it off and back on and it's been fine ever since.
