I don't have the S15-B, but I do have the S15-D, which is just the same thing with deep red rat fur instead of oiled birch. Awesome, awesome cabinets, but they're not going to reproduce low B very well at all. High-pass filters are a must if you're going to be running high wattage through them. I ran a Mesa Carbine M6 with a Rane parametric EQ (has low- and high-pass filters as well) in the effects loop and two of the Bag End cabs. Scary awesome...the amp is very very clean and precise, and the cabinets add just the right amount of midrange growl and grind.
It's been too long ago, but back in the day I had an EV 2x15 cabinet loaded with EVMs. I think I powered that with an Ampeg V6B. My playing and my ear both sucked significantly worse back then, so all I can say is that the sound was roughly similar, but it was way too heavy and I didn't feel much joy for it. I might be happier with it now and give it a better review, but I STILL wouldn't like schlepping it around. Of course, a pair of TL606 might be easier to move around than a single dual-speaker cabinet.