I use my Mullards in V-1 and V-2.
This is where the tone changes will be most affected.
I have also changed so that I am using Mullard 12 AU7's to get less distortion.
The Einstein has so much distortion on tap and I never need all there is, that I can get more tone from less powerful tubes and control the distortion amount better.
My next step will be power scaling, as I want the ability to get power tube distortion, which I feel gives me more of the tone I want. Too much pre-amp tube distortion, to me, leaves not as much clarity in the overall tone of the amp for my personal usage at lower volumes, where I want the amp to sound more cranked, but still clearer sounding at lower volumes.
In other words, I want the tone and feel of a fully cranked amp, but I do not want the volume. However, to get the power tubes to distort, means cranking up the master volumes, which makes the amp so much louder then I can use, so I cannot achieve my desired tones with the feel from the amp that I want.
Right now, I am using a Xotic BB which is o.k., but it does not achieve for me, the desired tones yet. It only comes a bit closer.