I've noted the same thing... I like the BAT sound (tube pre + SS amp) and several of the Mc amps, including the 402 & 602.
I've not tried the vk75, but did own both the vk60 & vk500 w/BAT pk... and a vk5i. The 5i & 500 was just super. Upgrading the preamp to a better one, was still better. My sole regret here is selling the vk500.
I think there's one for sale now too. The vk 500 w/BP is better IMO than the 402, and is neck and neck with the Mc 602, with the 602 coming in by a head.
The one thing I've noticed on previous BAT amps is that the SS and tube versions don't sound anywhere near like they should. the SS sound IMO what many tube amps are like, and the BAT tube amps are closer to what many SS amps are like. (Using oEM tubes), but are far more open than SS too.
I feel you this way... If you like what you are getting... Keep doing what you are doing... get a BAT amp.
The Sophia IIs do respond well to having more power, but it's not necessary to have gobs of it unless you want to.
Between the Mc 402 & BAT 500... I'd do a 500 w/BP every time... even in SE config, it's very good. XLR is better though.