If NOS pre or power tubes became unavailable altogether, what new tubes would you buy?

For what it's worth, the CV181 is NOT electrically equivalent to a 6SN7.  If you replace a 6SN7 with a CV181, it is bound to sound different, because the CV181 is operating at a different part of its performance envelope.  But people do it.  Have fun.

Raul, I think one reason that SS has taken a back seat to tubes at the higher end of the audiophile spectrum is that most of the SS gear to which we are exposed is built to a (low) price point, and if you look inside, you see crappy capacitors, bad layout, fail-safe circuit designs, for example using over-size electrolytic coupling capacitors, that assure mediocrity.  There are only a few SS products built purely for max performance with cost no object.  Perhaps you should start a thread to discuss this phenomenon and name some of the best SS products currently and previously available.

@lewm,
Thanks for clarifying that not all 6SN7 *types* are identical. I was merely trying to assure him that he wouldn't be applying plate voltage to the grids or heaters. Electrical variations (as I mentioned) do vary from tube to tube. Of all the 6SN7 types there's only one to be leery of and that was a mil-spec RCA VT-231 that pulls significantly higher filament current and could stress the x-former tap. 
Yep, it's important to find the tube's idea point on the curve, which depends on your circuitry. I (and the design used in VTA/Tubes-4-Hi-Fi gear like about 45% for the 6SN7s I use but it's not a magic number. I sure wouldn't go much above 65-70% for such a low Mu tube.
If John Bedini could build the "near perfect sounding" amp out of sand components 30 years ago, I am sure there are ss pre-amps and pwr amps out there I'd like better than my tube lash-up. But as you say, most of the new stuff has crap fail-safe circuitry and cheap parts. Even on the tube side a lot of very expensive production gear uses junk. Why McIntosh went with the EH tubes in their driver section I'll never understand, when for a few bucks more . . .
As to s/s vs. tubes, that horse has been beaten to death. Whether tubes or s/s, the sound is going to be far more flavoured by preamp components and the amp's driver section than the honkin' amp, at least according to the all-knowing myself :-), and might be worthy of a thread if there ain't one.
Cheerio,
-d-

Dear @jbhiller : No one has to worry about tube sources because always exist better alternatives that are almost really unknow for many of us and that's why I posted here.

Is clear that many of us want to stay sticky on tube electronics and maybe because many of us already losted the " adventure " esprit of a human been. Looks like many of us already losted the " quest " to find out what to do and how achieve a true better system quality performance level in favor of MUSIC.

Certainly rolling tubes is not a true answer to but try to learn how to look for true answers.

This is what a gentleman posted in other thread :


"""  the most accurate phono cartridges sound more like good digital . This makes me think some people do like pleasant distortion  . Remember ignorance is bliss until you have heard the difference . """


" until you have heard the " true " difference ": we can't have a true valid opinion in what we have not valid experiences.


Regards and enjoy the MUSIC not DISTORTIONS,
R.

My mistake, it has to be this way.

"  we can't have a true valid opinion if we have not valid experiences. "

R.

@rauliruegas 
If you can't identify at least one piece of gear you believe is better than whatever other piece of gear (or better yet, the entire signal path) you've heard, as I have asked you for, then I suggest your opinion reflects the depth of your experience. C'mon, give it a try. I won't flame you. I just want to know what experiences you are basing your opinions on. Perhaps I will learn something.