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

The most consistent new tube I've used over the past 8 years has been Shuguang Black Treasure ( KT88, CV181-z, 12AX7 LS ) and Psvane (12AU7, 12AT7).

Shuguang Black Treasure:
http://psvanetube.com/wordpress/purchase/shuguang-treasure-series-vacuum-tubes/

Shuguang Custom 12AX7 LS, Psvane 12AU7, 12AT7:
http://psvanetube.com/wordpress/category/review/feedback/

There is no modern day equivalent to the NOS Hammersmith code Genalex KT-88.

Dear @enginedr1960 and friends: Comparison means not a few hours but at least 3 months in a row with full SS sytem and then come back to tubes and compare it. In those months is very important to attend as often we can to listen live MUSIC in a nearfield situation, this nearfield issue is important because is the way the recording microphones are in place during it and the target is to be nearer to the recording nearer on what the micros pick-up.
To make a serious comparison is critical to have a proved/bullet-proof whole evaluation process and to know in specific what to look for during those evaluation tests.

The tube overall subject is a very sensitive subject every time I " touch " it and the problem is mainly because many of you are living for many years in the " tubes's ghetto "  ( the only difference is that there don't kill you, only kills the MUSIC. ) where you never ask to stay there the corrupted AHEE just put all of you there ( in the same manner I was there for years. ).

All the ones inside that ghetto are victims of but all of you have a true advantage over the second world war: you are totally free to go out and I know sooner or latter all go out and the corrupted gentlemans that are the owners of that ghetto will pay for what they did it with all of us.

We only need to learn. They take advantage of our very high ignorance levels in that subject and that's corruption.

Btw, @toddverrone: you are rigth but I never said invented nothing and about the " horse " that's a privilege that each one of us have. never mind, agree with you.

Regards and enjoy the MUSIC not DISTORTIONS,
R.

Everything distorts, from your gear to the room to the shape of your ear to the engineers and mics. I believe well-designed tube gear distorts best to my liking; with the close exception of a well cared-for S/S Bedini, it's preferable to SS distortion.
As to NOS v. modern issue, I've never had the pleasure of the Hammersmith KT-88s, but have had my run of antique NOS TS-6550s, Mullards, Brimars, Philips and the like, and the modern stuff from eastern Europe and Russia.
I believe the Chinese have gained the upper hand in sound quality for KT-88 type tubes if you stick with PSVane or ShuGuang. Both have factories in Changsha. My favourite of that lot is PSVane's top-end Mk II Treasure series. As for signal Tubes, PSV's top-end CV-181s will blow the skirts off any 6SN7 tube, NOS or otherwise, I have ever heard. But they're big bastards, almost as large as output tubes. so that's a consideration.