Finally got one of these, the TFB420. Bought it used at Atomic Music. As a longtime Amplified Music Products BH-420 user (make that fanatic) I've been curious about them since they were first talked about. Bottom line, this is the real deal. As hard as I found it to be to imagine something that actually improved on my AMPs, I hear the improvements. They're subtle but they're there. I would've been impressed if it just sounded as good as my BH-420s. I haven't taken it on a gig yet but so far in the store and at home this amp sounds great. Ran it through a coax Bag End 15 at the store, sounded very nice. At home through my newer 1-12 Nahas tiltback it's ridiculous. Huge sound, big yet tight, very articulate and open sounding. Playing my Brubaker K5B Xtreme with both the Bartolini NTMB and Aguilar OBP-3 preamp modules was way too much fun, especially the Aggie. It weighs practically nothing. My AMPs aree in the low 20 lb. range so they weren't exactly boat anchors. This is noticeably less. Like my AMPs, I ran the EQ and tone controls flat. Just turn it up and play. The variable Enhance control is much nicer than pushbutton on the older amp, which I found to be useless. The rear panel mods are nice and useful. The biamp crossover is gone and good riddance as far as I'm concerned. With full range sound like this who needs to biamp? I was always amazed that my older AMP amps had no external fins or fans and were practically silent when I wasn't actually playing. The case would warm up, especially if pushed really hard (with ineffiecient cabs for example). The TFB with the switchable fan (nice touch) damn near runs cold. I would imagine that would only help to prolong the lifespan of the components. OTOH I've been gigging for more than 10 years with my original AMP with no issues other than a power switch that stuck on (it even failed in a good way... how cool is that?) years ago. My friend Preach calls my AMP "the Ogre"... it's a tone beast. He just found and bought his own AMP BH-420 yesterday and he's in tone heaven. We put that through it's paces, again at Atomic Music, through a 2-12 Nahas cab rated at 800w at 8 ohms. With both gains well below 50% it was ridiculously loud. I'm keeping my AMPs, still love them. The TFB will go on my next gig and I fully expect to be floored. I think I have a new main amp, like the old one Highly recommeded.