IF you can drive your speakers adequately in the Class A amp's power envelope and your listening skills are developed sufficiently to hear the subtleties brought by Class A amps, and you are actually paying attention to those subtleties, then a Class A amps is a no-brainer. The best SS amp I ever owned was a low power Class A amp.
BUT usually the difference between a Class A amp and a Class A/B amp attributable to the difference in class alone, sonically speaking, is not great and can be dwarfed by the selection of other components in your system including some ancillaries, so buying Class A amps usually is profitable only if you take as much care in selecting other stuff, including room and set up considerations.
I agree with newbee's notes above... a Class A amp brings a different presentation (more musical IMO) where even one can be fooled of hearing a SS or a Tubed design (this happened to me when I had a Gryphon Anthileon amp)
But... speakers play a major role on not having the sense of lacking of additional drive and dynamics... I am not familiar with your Verity speakers so I can't comment there, I drove a quite easy load with Avalon while I had the Gryphon and reached a nice level of music reproduction.
I have been enjoying the Verity Audio Parsifal Ovations for several months now, driven by the Luxman 509u integratd amp and Luxmn D-06 cdp. As a system it sounds wonderful, and the electronics match well with the speakers.
I enjoy classical music (piano, chamber) and jazz. I listen to a lot of solo piano, and I often feel like there is an actual Steinway D playing live in front of me.
Interestingly Redbook can sound as good as SACD to me when it is well recorded. Some Chandos and Hyperion recordings from the early 90's sound superb.
To be honest, I have stopped listening to the equipment and worrying about individual components. I now lose myself in the music and thirst to hear more. This is a system that conveys the essence of well played music.
It seems this is a common dilemma with those interested in the Luxman integrated amps, whether it be the 509/590 or the 505/550, few have heard both. I purchased the 590A II back in January and like you I am very pleased. Between the 509 and 590, functionally there are trade-offs both ways, such as, the 509 lacks a remote, this is a big deal to me; for the 590, as you state, it runs hot and for some 30 watts isn't enough, although it is a very powerful 30 watts. I was specifically looking to go Class A.
In talking with the dealer I purchased mine from and asking about the differences between the A and A/B units, he feels it depends on the speakers one uses.