Octave v70se OR v80se

That is a pretty large room for an amplifier with such limited output (only 70 watt *peak*). Unlike some here I do not believe that competently designed amplifiers used within their specifications have a sonic signature (and they most certainly should not). What I have experienced is that an amplifier without enough power does degrade the sound, by clipping and compressing the signal in more dynamic music.
One issue, however, that can degrade the sound is a load dependent frequency response. Tube amplifiers in particular suffer from this problem, with a response and hence a sonic character that can deviate far from neutrality/reality. Here, the definition of perfection is a response that is flat within 0.2 dB over much or all of the audible range. I am afraid a test of another Octave amplifier in Stereophile showed that at least that model suffered rather badly from this problem: https://www.stereophile.com/content/octave-audio-v-40-se-integrated-amplifier-measurements
Almost any solid state amplifier would be better than this, and such amplifiers do not even need to cost much. I recently bought a 2x250 watt Yamaha p2500s pro audio amplifier, and it beats this Octavo by a very wide margin, and for only 300 euro (about $350, yes indeed). See here for a test of the bigger P3500s: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...
I am sure it will also sound far cleaner because of its hefty power output. I think it is time for a rethink. And if you want to spend money, get yourself a Benchmark AHB2 or a Bryston.

I also encourage you to follow @inna 's advice and call Octave. Many manufacturers are reasonable and you will learn a lot. If you find the person(s) you speak with to be over the top, then adjust accordingly. 

I would specifically want to know how the Super Black Box paired with the V70SE performs vs the V80SE alone.

You may also want to reach out to the reviewers of both directly.

Both the V70se and V80se are excellent IA's. I used to own a V70se and later the V110 with the black box. I also had Dyn C1's and later the Signatures. I had an in-home demo of the V40se for a week. As you move up the line there is a bit more control in the music. IMO the black box or super black box is a must. Lowers the noise floor quite a bit and provides a touch more headroom. I have not heard the V80se only the V80. I got out of tubes just before the V80se came out. The V80 had better transformers. One nice thing about the V110 is it has a switch on the back to change the plate voltage down to accommodate tubes like EL34's 6550's and KT88's that way you are not limited to KT120's. Honestly I hated the KT120's. I'm guessing the V80se also has it so your not limited to KT120/150. I did find Ei KT90's worked great and sounded better at the higher plate voltage.
Per Andreas the super black box was designed for speakers with multiple drivers. I never tried the SBB with my C1's but my friend with the a V80 - BB and Dyn Sapphires demoed a SBB. the difference was IMO was huge. So I can't say what gain would be had with the C20's.

@david_ten I would say the V80se would out perform the V70se with the SBB.

The beauty of tubes is if you ever want to change up the sound signature just swap out some tubes instead of buying a new amp. When I had the C1's I rolled many different tubes and found the original Tung Sol 6550 black plates sounded the absolute best to me and my dealer. BUT when I decided to upgrade my Dyn C1's for Raidho D1's I hated the the TS 6550 bp's. I liked the Ei KT90's much better with the D1's. Now with the Dyn's the V70se or the V110 never ran out of 'steam' when pushed extremely hard. But with the Raidho's they would only when pushed hard. Maybe the SBB would have helped.


So I would go with the V80se and consider a BB at a later time.

@xti16   Thank you very much for your detailed response. 

Given your experience with Octave, do you have any thoughts on the other German tube integrated: Lyric Audio? Thanks.

No I don't. I think another thing that has to brought up is the protection the Octave has to offer and soft start circuitry. It's second to none IMO. I had a few tubes 'arc over' and NO damage to any circuitry. Biasing tubes is very easy too. If I had a complaint regarding the V70se or V110 is swapping out the 'little' tubes. Hard to get a hold of. Not a problem with the V80. Another feature that could be taken either way was the auto shut down to standby when no music is present for about 10 min.