Hi THChrist,
Well if all you really want to do is play the guitar then you can waste so many years trying to perfect an amp (Glass or Sand) you may forget how to play the instrument by the time you finish.
I make a personal point of not bothering very much with *One Off* builds/sites that claim or even imply they found the holy grail circuit.
Unless they have evidence of there inventions being used by live working musicians or have built quite a few.
The amount of times I've got excited over circuits at home only to find in real world working situations they never deliver.

Want to see my shed full of land fill circuits (spare parts bin now)

In close to 30 years of messing with circuits only 3 or 4 of my inventions are worth a mention. (All posted here I should Add, check under schematics) I would not be so cruel as to post circuits that I knew had possible shortcomings.
You mentioned power tube sound so here is a little trick I did many years ago you might wish to try which will open your eyes about powertube sound.
I simply took a small little 20 watt SS Amp and wired a series lamp limiter into the Mains power cord which produces quite convincing power amp compression.
Caveat; The Amp circuit needs to be very simplistic for this to work.
i.e no onboard digital FX and fancy switching circuitry.
You loose some wattage but the saggy compressed sound is very reminicant of tube power stages.
At times I wish I'd kept that litte amp it was so much fun for small gigs,, as I
needed no pedals,, just a straight rock sound with nice rattle and comp when driven hard.
The draw back, just like early small valve amps they sound great but only at one Volume level.
IMO the difference between a good or bad amp (Any type) can be mostly put down to
tone shaping. i.e how and where in the circuit these tricks are implimented can make
a massive difference.
Just hanging the Marshall value resistors off a semi conductor wired up the same way
shows little understanding of how to make good amplification.
I won't mention names but a lot of fet preamp circuits have become so popular because they use close to exact values as those used on some famous Valve circuits and again they are far from ideal as good *Reliable* circuits.
Yes they work but often the SNR is horrendous because they just hang 1 meg resistors
off every gate like a valve Amp and high gain on high imp = massive noise.
Try reading some of this stuff before you travel down the complex path.
Humans have a habit of insisting that complex problems must have complex answers and
often even the experts can miss a really simple idea.
http://www.amptone.com/truesecretofamptone.htmA bit dis-jointed in places and rather long winded but it covers a lot of questions
that folks like you ask.
I may not agree with all of it but I'm sure it won't take long to catch on.
anyway I'm just rambling on so time I went.
ps, I only speak 2 languages, English and Oztrayland

Phil.