My concern with the Continental is two fold: heat issue and battery live. 95% of my listening is on the go, so my rig is nestled in a messenger bag most of the time. Stacked, even with bands acting as spacers between components AND being inside a closed bag might cause some heat issues, degrading the overall battery life. The HD 650's certainly offer the nicest presentation out of all my cans, but being open they're not well suited for use in public (I like to drive them ;-) )
Listening to a variety of music with an emphasis on classic rock I wonder if the smoothness of the V3 won't be lost in the mix. My source materials are all.wav files of Japanese masters, Audio Fidelity, MFSL, etc. I suppose the benchmark for me is to have Steely Dan sound fuller than it does on the National CLAS -R pairing.
The one thing that sticks out in my mind is the ALO reply that the Rx-MK3 B+ has a more clinical sound: do you find that to be true with your set-up?
There will definitely be the issue of heat with the Continental after several hours of play - especially if it is enclosed in a bag. Whether that will make the battery life shorter is anyone's guess. I guess it also depends on the weather Over here in the tropics, the day temperature is enough to kill me
As for the sound, I know the RX-Mk3 B+ is definitely more powerful and maybe more neutral sounding (compared to the Continental). I would consider the sound of the Continental quite similar to the RSA Intruder (not sure if you have heard the RSA before). To me, the Continental is not all that warm sounding for a tube amp Since I use mainly sensitive iems, the hissing from the RX Mk3 B+ is a turn off - for me.