When people say oomph... They probably mean those unusable sub bass frequencies that muddy up the entire mix, leaving the kick drum buried. Also due to the wavelength of bass frequencies being longer than higher, they would be more pronounced at the back of the room.
I've had both Class D's and your back breakers, i've pony sounding amps in both fields and good sounding amps from both too. That's why you should always try before you buy.
Another problem is that a lot of bass players just don't know how to EQ their amps properly which in turn gives poor performance and poor sound from the amp.
Just my 2 pence rant