ARC D-115 use half of tubes

Some amps can have half the tubes removed and work fine (Atma-Sphere's, for one). ARC amps cannot.

I own a D70MK2 and I think it is actually a better sounding amp than the bigger D115! The other plus, which I think a lot of tube amp users forget...or don't truly understand, is that the more tubes, the more heat and more potential for failure.
Some of the monster ARC amps with what....16 tubes or more, are IMHO just ASKING for trouble!
Lostbears, you say your D70 was thin sounding!!! Wow, you must have had one heckuva mismatch with your speakers...BUT don't blame the amp for the mismatch. IF you have another chance to hear a well set up D70 in a synergistic system, I suspect you would take back your suggestion about the D70 vs. the D115.

I had a mk1 version as I remember. It was a very nice sounding amp but seemed to run out of power very easily. Actually I sold the amp to a buddy who I believe still has it packed away somewhere. I had a pair of monitor type speakers at that time, I don't think they were terribly inefficient. It was 25 years ago and I just don't remember the model anymore.

As I said I replaced the D70 with a Classic 60. The Classic 60 was also rated at 60 watts but never seem to run out of power or sound thin. I later bought a pair of Soundlab Dynastats which I am sure were far less efficient. The Classic 60 still never seemed to run out of power in the same way. Granted the Classic 60 is a Hybrid design and not a pure tube amp.

I used to own a Classic 60 before I owned my D70Mk2. IMO, the Classic 60 is not in the same league as the D70Mk2. While the Classic 60 is a good amp, I don't think it has anywhere near the midrange purity or the ability to float the soundstage like the D70Mk2. OTOH, the Classic 60 is easier in some ways to get running optimally, plus it is less demanding on the quality of the tube. Lostbears, unfortunately I strongly suspect that you never truly heard what your D70 could sound like.

Use all the tubes in your D70mk2.