Kool39,
Most likely it is the marketing...
Adcom was most peoples first exposure to separates.
Aragon on the other hand you needed to look a little deeper to find. IMO
Regardless, in the used market the 555 is still able to be used to bridge to mono and I believe is rated at higher wattage than the Aragon... like that matters.
Protect your hearing!!
Joe
Custom Audio LLC