My speakers have 12" bass drivers and 12" ABR which probably means l can hear how it is more than most as most bass amps have 15" drivers.
Now I'm really confused!?!
I assume he was referring to live equipment when a combo amp and speaker cabinet is sometimes just referred to as an amp, and indeed bass cabinets tipically have 15 inch drivers, sometimes larger, as do PA rigs. For music normally played live through such systems the greater inertia and so slower starting and stopping of the cone is inherent in the live music, so may not sound wrong at home. To me the bigger PMC speakers, with 12" bass driver and larger, and very likely the big ATCs, make a lot of sense at least for rock music - and I've listened to the MB2 which has a does have an uncanny ability to sound like a live performance, and not just on rock music, handling classical very well, too, from the visceral feel of the bass to presentation of fine detail. Tiny cones have a real challenge to shift the amount of air needed to reproduce deep bass at realistic levels - a pair of 6.5" drivers have to move 3 or 4 times as far in and out as a single 12" for the same sound level. Of course it doesn't matter to anyone preferring their music without the full bass, but that appears not to include the OP.
It is interesting that the power supply should limit the bass in the way described: on a power amp my expectation would be for a better PS to enable faster and/or greater delivery of current, which would help the cones follow the recorded sound's shape more accurately as long as they remain within their movement limits - but maybe with a preamp the effect on control is more to do with assisting the amp to do whatever it does to create the 'Naim sound', and that may simply be a sound the OP is less keen on.