There is no such thing as "SS" or "Tube" sound. It is simply the character of an amplifier. You get "warm & fuzzy" SS amps and "Bright" tube amps as well.
Some terms are misleading.
Your description is also a bit odd. You say you get "undefined" bass with the Classe amp but "deep tight bass" with the ARC amp? I would say its the other way round. Usually tube amps have a hard time controlling woofers during lush bass passages. This might make them sound "warm and fat".
The Classe amp could have better control over the ML speakers woofers and thus cause them to sound a bit "thin". This is simply that the bass is not as "loose" as with the tube amp. The Classe amp also might be overall bright in the treble regions.
Try auditioning a hybrid power amp or a tube pre-amp with the Classe power amp.
Some terms are misleading.
Your description is also a bit odd. You say you get "undefined" bass with the Classe amp but "deep tight bass" with the ARC amp? I would say its the other way round. Usually tube amps have a hard time controlling woofers during lush bass passages. This might make them sound "warm and fat".
The Classe amp could have better control over the ML speakers woofers and thus cause them to sound a bit "thin". This is simply that the bass is not as "loose" as with the tube amp. The Classe amp also might be overall bright in the treble regions.
Try auditioning a hybrid power amp or a tube pre-amp with the Classe power amp.