I have to agree with you - some drive pedals work better than others. I've never like the way the Tim sounded through the Mark V:25 Fat setting but love the tones of the SILT, Tube Driver and H90 drive algorithms. The versatility of these little beasts is impressive.
As you've discovered, the DI output of the Mark V is dependent on Master Volume settings. I use a Radial X-Amp to boost the signal when using lower MV settings.
Again, my experience is different. You keep mentioning what you've read, not what you've experienced. What I've read by most manufacturers is any mismatched combination is not recommended. What I've experienced is most modern tube amps are designed to handle that stress.
Some additional...
I understand you're going by what a single manufacturer prints in their manual about their product.
I'm speaking from experience as a former touring tech and an electronics engineer. What has your experience been?
Did you know most tube amps short their signal to ground (0 ohms) as a...
I think you're confusing tube with solid state amps. Never safe to connect a ss amp to a 4 ohm load if the amp isn't 4 ohm stable. General consensus (since the '70s for me) is the basis of my post. I've done it many times with many different brands over the years - I've yet to lose a transformer.
16 ohm tap will do a 16 ohm or 8 ohm cab,
8 ohm tap will do a 16 ohm or 4 ohm cab,
4 ohm tap will do an 8 ohm or 4 ohm cab.
I've been following that rule since the 80's and have never had an issue.
Any pedals? If so, what type of power adapter are you using with your pedals? Some of the adapters out there are notorious for high-pitched noises especially noticeable with bright amps and/or bright settings.
Quality, custom built equipment for the touring musician is rarely cheap. The adapter is still cheaper than a MIDI controller or modding your amp. They warranty their work and there's no danger of killing the control circuit of the amp should you mis-wire something. My experience is - touring...
I wouldn't worry about a balanced preamp tube for V6. I've never been able to tell a difference in tone in that respect, though some say they can. I wouldn't do a wholesale retube either - try switching individual preamp tubes with a (known) good tube to see if it's tube related. (Probably is...
Tone, portability, and lower stage volume. My 4x12 days are over. It took a little getting used to, but the subsequent gain in overall volume control is wonderful to these tired ears. When mic'ed, that little 10" speaker can sound huge!