Luxman m-900u owners - quick question

I am currently using the M-900 U , just turned it off. I had the preamp first  and just got the amp 2weeks ago  and still have questions. First if a AB amp has to run so hat why design it in such way that it delivers only 12 or 18 in class A. Is it just to adopt the hyper-modern look and restricted ventilation?The  Amp sounds very detailed and solid  with no harshness  Still under evaluation with his Luxman peers . I am a dedicated Luxman fan This amp  is playing substitute to a pair of M-5 run in Vertical bi-amp( 1 stereo amp on the left the second on the R)
cannot afford 2 M-900 U now. !!! This set up alternates with also two M-05 100 pure Class A run the same way or at time two Accuphase P-102 .  I just got rid of two old  M-22  used in the same set up on the speakers that I have for 17 years the Piega. C-35 . Still evaluating . I do not believe in reviewer like statement best amp  ever At this level  great amps may differ in some points may be this is all there is to it at this level of High-end. Believe me the tonalité and the thightness of the bass and mid bass with the 30 watts class A Pioneer M22 is not something to sneeze at even at this level. My question any idea why this 900-U run so hot as a AB amplifier most good amplifiers have their first watts in A nothing new here Why it gets so hot?

I am currently using the M-900 U , just turned it off. I had the preamp first  and just got the amp 2weeks ago  and still have questions. First if a AB amp has to run so hat why design it in such way that it delivers only 12 or 18 in class A. Is it just to adopt the hyper-modern look and restricted ventilation?The  Amp sounds very detailed and solid  with no harshness  Still under evaluation with his Luxman peers . I am a dedicated Luxman fan This amp  is playing substitute to a pair of M-5 run in Vertical bi-amp( 1 stereo amp on the left the second on the R)
cannot afford 2 M-900 U now. !!! This set up alternates with also two M-05 100 pure Class A run the same way or at time two Accuphase P-102 .  I just got rid of two old  M-22  used in the same set up on the speakers that I have for 17 years the Piega. C-35 . Still evaluating . I do not believe in reviewer like statement best amp  ever At this level  great amps may differ in some points may be this is all there is to it at this level of High-end. Believe me the tonalité and the thightness of the bass and mid bass with the 30 watts class A Pioneer M22 is not something to sneeze at even at this level

By looking through the top I got a sense of the size of the heatsink but it looks like they wanted the entire chassis to radiate the heat. It beats the M—05  (100 Pure A )that I still love :sweetness over details !!

By looking through the top I got a sense of the size of the heatsink but it looks like they wanted the entire chassis to radiate the heat. It beats the M—05  (100 Pure A )that I still love :sweetness over details !! By the way I don’t think driving any amp in this class with any DAC directly is a great Idea