Whats the FATTEST sounding Tube amp to warm up Lean speakers?

I agree on #4, no power conditioners.

They cannot fix a difficiency in an amplifier's design. The resistance of the series chokes adds to the resistances in the primary circuit. They add yet another power cord and socket,more resistance. Here we are trying to lower the resistance in the primary and then go and add perhaps more than we have subtracted.

Do any power conditioners give their effective series resistance?

@ramtubesNot all power conditioners are the same!! However most offered to high end audio seem to be so much junk. There are some that have no series chokes at all, but still are able to provide a pure sine wave at full power, which can be quite a lot.

You might want to take a look at some of the Elgar power conditioners like the 3006 series and you will see what I mean.

I heard amazing things about your Amps and i am close to trying your s30.

Usually people use the S-30 with the TSM. The VSM needs a bit more power so the M-60 has been the preferred amp for those.

Sure- the Jouls is known to be a favorite match by the designer, however, im trying to counter the speaker's philosophy here, so it is my thought that the Jouls is actually going to emphasize the leanness of the speaker, not counter it. Or Bobby P wouldn't have used it.

I don't agree with this statement at all!
Bobby was not going for a lean sound, and I've not had anyone report that to me when using Merlins.
How do you have the Merlins set up? Are they firing into the long dimension of your room or the short dimension? Normally to get the best bass, the speakers will be firing into the long dimension.

Are you using the BAM? If no, it will sound lean.
Did you check to make sure the phase is correct? If one speaker is out of phase with the other, the bass will be gone. Try reversing the phase after playing a track with good deep bass and see which way has the best bass.
Often you can move the speaker back, closer to the rear wall and get bass reinforcement. You may lose some dimensionality though.  Similarly, the listening chair can be moved back to a room boundary to reinforce bass.

Some amps just don't play bass all that well and I can't speak for what you have right now. But as you know, Bobby designed the speakers to be easy on tubes and he really liked OTLs- on the right speaker they can play bass better than most tube amps!
Finally, long speaker cables and tube amps don't tend to play bass as well. Keep your speaker cables short- 8' might be the longest you can run and 3' would be better. Make sure your connections are tight too.

The most popular speaker for many years with our M-60 amplifier was the VSM. Very nice match and we showed with Merlin at several CE Shows.

But I would not call the amplifier fat sounding (which usually describes an excess of 2nd harmonic distortion which our amps tend to lack). It just sounds natural.