Found your post a little hard to respond to but FWIW, Ian's Rave.
Item 1) Fundamentally the input stage of any Git. Amp has one master requirement - maximum clean gain. Why? because we want to get the guitar signal level up to a level where it can overdrive subsequent gain stages. The guitar itself has insufficient signal level to cause overdrive of the input stage. Pedals can of-course change this and boosted output pedals can cause overdrive of the first stage. In a High Gain preamp this input stage is the most critical with respect to noise (hiss) and in fact I am now designing with a JFET MOSFET Cascode input stage for high gain preamps (with tubes following of course).
Item 2) 2nd harmonic. - 2nd harmonic off a C is a C an octave above. Because Harmonic Distortion is produced by the same mechanism as Intermodulation Distortion (you can not have one without the other) then sum and difference frequencies are produced with a respectable content at the C an octave below. Add that to the physco-acoustical action of the brain of filling in the "missing" octave below bass note.
If you plot voltage in vs voltage out (at the anode) then you have what we eng. types call a transfer function.
Any deviation from a straight line indicates distortion and the curvature of the line indicates the order of the distortion. Gently curving lines indicate low order mostly 2nd harmonic distortion. Sharper curves indicate higher order distortions. Why is that important?
2nd harmonic of a C is a C an octave above
3rd harmonic is extremely close to a note which forms the C Major chord.
While 2nd harmonic distortion adds "warmth"
3rd harmonic distortion adds "Edge"
we do not need to go to far before we run into problems:
The (IFRC)7th 9th and 11th harmonics are musically "quint" in that the bear no relationship with the original "musical" note.
to conclude the rave - the triode amplifier is the most linear amplifying device ever invented by man and so has the low (mostly second harmonic) distortion we want with an absence of higher order harmonics.
3) SS too much gain - gain in an SS circuit is so circuit value dependent that too much gain is a tricky arguement.
As an overall argument however we get back to basic philosophy - an ideal amp is a piece of wire with gain.
The main SS Amp design philosophy is "infinite Gain/a little less Infinite Feedback" to give a linear amp. The more feedback the sharper the transfer function curves and the higher the order of the distortions produced.
Why should I worry about that?
5% of 2nd harmonic distortion sounds great.
0.01% of 11th harmonic is fingernails down the blackboard stuff.
Don't produce them in the first place (ie a triode gain stage) and roll off the high frequency response in the amp to make sure anything at the 11th harmonic which does get produced is killed by the following circuits.
4) Clean SS disadvantage - WOT? see above.
The absolute best input stage for a high gain preamp is a JFET/MOSFET cascade.
The absolute best input stage for a medium/low gain preamp is a 12AX7 or a 6SL7 or a various triode strapped pentodes.
Yes the basic curves of the transistor are far inferior to the triode gain stage but after we peg back its gain (with feedback) to something similar to a triode then that feedback runs a long way toward linearising the transfer function and giving us the gentle curves/low harmonic distortion order we want. EXCEPT at the limits of the power supply when hard clipping happens.
V5) Sorry I've lost the plot
Hope there was something useful in my "rave".