Vfet / SIT Amplifiers

@atmasphere 
I see some assumptions on your part which could probably come from a misunderstanding.

First off, I love the SIT-3 amp. Low volume, high volume, I love the amp all the way. What C-1 does, it allows SIT-3 to play louder (if and when needed), but SIT-3 does extremely well at even the lower levels. 
In short: at no point I voiced any dissatisfaction with SIT-3, but emphasized the synergy between the vfet pre and vfet amp.

About C-1: my unit is fully restored and with SIT-3 I use it with all tone controls defeated (including loudness). If you have not heard the line stage of a C-1, I wish you have the opportunity to do one day. I am also thinking that if you like tube preamps, you will be in for a pleasant surprise listening to a vfet preamp :) 
Tone controls in the C-1 come in handy with certain amplifiers, or to tune in the room. I did not find it necessary to use any of the tome controls with SIT-3.

About the simplicity of design: The simplicity of design can be argued back and forth. Designers have learned since the 70s and are able to simplify modern designs. Also, certain components are built better today then were built in the 70'. All that is true but also many things done in the 70' have been forgotten. 
In the case of Yamaha, most of the complexity comes in the form of circuit protection of sorts...quite crazy in the case of the B-1 for example, or tons of features in the C-1 pre, which at first glance is the anthesis of "wire-with'-gain".  Some features of the 70's amplifiers are probably there just because the marketing department wanted them to be there. Some of these features can be defeated or carefully bypassed. Additionally, after 40+ years of use, some of the original ancillary components are at the end of their functional life and can be substituted for better components built today, and one can use the 70's vfet amps the proper way ;) and ensure that it would ran for many more years to come.

Making a side note here: complex or not, these 70's amps run for 40+ years already. I giggle when I hear some manufacturers marketing claims related to 20 years warranty as if that would be of any relevance....yet you see many consumers basing their opinion of brand preference based on such irrelevance.

What is important in the end is what the amp sounds like and will the amp be around long enough for the owner to enjoy it. That is simply the ultimate test, right?

One could argue for instance, that SIT-3 has relatively high THD, right?
But if most of the harmonics are of the even kind and if overall the amp sound as good as it does, how important are the technicalities?
Same goes for the Yamaha or Sony amps...yes more stages, NFB, etc...but if the amp sounds good, why do technicalities matter?

As far as I know, there is no scientific proof or empirical evidence that just for being simple, it must also sound best. Since we are talking about Yamaha, one of their other statement pieces, the MX-10000, is one of the most revered amps of all times. Yet, it is one of the most complex designs I am aware of, has stupid low THD, but in the end, it sounds phenomenal and can pretty much drive any load speaker. 

I hope I was able to clear any misunderstanding. I am a fan of anything that sounds good to my ears, agnostic of how complex or simple it was built, in technical terms :)