Classe DR-15 amplifier compared to Classe Dr-9

I have two Classe Dr-15 amplifiers used in bridged mode and was wondering if they compare favourably with the Classe DR-9's. I find the Dr-15's to sound really good, not as fast as today's amps but otherwise very little to complain about. If the DR-15's compare favourably to the Dr-9's I may forget about replacing them. Any input would be appreciated. Thanks.