6N23P Silver Shield 74 SWGP
Unfortunately one has already gone bad so I've had to remove them and go back to the stock 6N6 tubes
Thats unfortunate. I've had similar issues with the 6n23p's. They seem to be pretty fragile and tend to conk off very fast. I recently went ahead and got myself 74 reflectors - grey shield, 74 reflector - silver shield and 75 voskhods to compare with my 75 reflector - silver shields.
I would say that my system borders on the neutral. Depending on the input tubes on my mp-d2 the sound get warm or neutral or cold, which I think is as neutral as it can get in my small room.
I found the 75 reflectors to be a bit warmer than the 74's with bit more zip up top. But I think the 74 reflectors are definitely not cold. I would put them neutral with just a hint of warmth. In terms on overall compatibility in my system I would rate them as 75 voskhod > 75 reflector > 74 reflector silver shield > 74 reflector grey shield. I think both 75 voskhod and 75 reflector are equally good. In my system, I actually prefer the slightly more accurate tonality of the voskhod - possibly because of the beryllium tweeters on my speakers.
I consider both 6H6p and 6H1p to be also on the warmer side of the spectrum.
What I am really enjoying now are 12at7 tubes. Got myself some Siemens Ecc801s, E81CC and ECC81 tube recently and the tonality is to die for. If your amplifier can handle the gain, these are the tubes I will recommend. If you can get either of the E81CC or the ECC81's - they are fabulous. Super detailed but not in your face, fantastic imaging, very airy. Bass is really good with a very dense tonality. Guitars, Pianos... sound so so good.
The sound stage of the ECC81 is perhaps not as wide as the 75 reflectors but definitely on par with 74 reflectors. Separation is good. The best of the lot is the E81CC (triple mica). It outperforms the 75 reflectors on every front. And the imaging is perfect. Tonality is so dense that on really bad recordings it gets a bit too much but even with spotify quality, these tubes are awesome.
I have not had any experience with the 12BH7's but from what I read, they should provide for a better tone that the 12au7's. I always consider the 12au7 family to be a little thin sounding - atleast the ones that I've heard.
Cheers