At the risk of drawing heat from this group: after reading a lot, I had a chance to buy a used B100R 15" combo as a back-up or for small gigs. I took my late-model Fender Rumble 100 along to A/B: if the Rocket wasn't louder and punchier than the Rumble, there was no reason to get it.
Verdict: Rumble 100 > B100 Rocket. Rumble's lighter, quieter, punchier and as loud, and least with flat settings in a dude's living room. Playing around it seemed like the Rumble actually could get a little louder without distorting, but I can't swear to that. (Also I didn't bring my 5 string, and the Rumble falls down on low B - Ds). So I didn't buy the Rocket. I'm aware of the limitations of the Rumble -- it's just my practice amp. But in an A/B (with a Spector fretless 4) it sounded as good as a lightly-used B100R. Actually to my ears the Rumble sounded a bit better. YRMV and all that, but if you're pining for a Rocket I'd suggest trying a newer Rumble. They're cheap, light, abundant, and much better than you'd expect. Just my 2c.