Hey DJC,
glad to hear you got the ADA/Boogie combo to work and sound to your likings. Boogies (especially the Mk series, and thats basically what your 2:50 is, the power section of 2 Mk non-simulclass amps) are mid-heavy. I guess that´s the reason for dialling out the mids in the MP-1.
Now if you run the Boogie with EL34 (which are way more mid emphasized than the 6L6 it was originally designed to run) it adds up.
With my old Fifty/Fifty I got the most awesome results running either TungSol 6L6GC-STRs (I also recommended them to Dante to run in his DC5) or TAD 6L6WGC. Both tubes kinda smooth out the top end a bit and give you a tad bit more spongy feel on the low end (as opposed to your standard Russian or Chinese 6L6 that have a strong and hard emphasis on both top and low).
I guess you´re not on the Djenty side of things so these would be my suggestion to get the most out of your setup.
FX wise (read you just have a pair of pedals in there) I´d either hunt down a Rocktron Intellifex (MP-1 plus Intellifex is pure 80s/90s bliss...plus the addition of Rocktron´s HUSH) or something like a Digitech GSP1101 to run in 4 cable method with the ADA, thus enabling you have more options in terms of FX chain...you can put front end FX where they belong (e.g. a nice Boost/TS up front for added cream/sustain or a Comp/Phser/Flanger up front of your clean patches) and Chorus/Harmonizer/Delay/Reverb in the loop/end of the chain).
Theres a GSP1101 plus Control2 up for grabs (dirt cheap) in the classifieds at Sevenstring.org (
http://www.sevenstring.org/forum/showthread.php?t=317695) (I have no connection to the seller....I´m a German living in Japan....).
All Boogie bashing in here aside....ADA pre's and Boogie poweramps are a letter-perfect match!
Best
SC