I don't remember him saying this was an SQ competition system. Yes, they sound wonderful, they are musical. They reproduce the sounds without distortion at high volumes. That's all I ask of them. Size of the driver doesn't automatically tint the reproduction of the sound... Smaller drivers simply take less motor and less power to be accurate. That is the only real difference. Soft part weight has little to do with actual sound. Size under high excursion does offer more chances for cone contortion, which is where the illusion of "big subs can't sound good" comes from. Well designed soft parts will reproduce the same sound in larger cones as they do in smaller.
EDIT: As a matter of fact, I can displace the same amount of air with less excursion than your 9510 did, therefore my subs would be less subject to tonal anomalies.