Since I don't know what you are using this rectifier in it is hard to recommend something. I went to a rectifier rolling session once and the best was a Mullard 5AR4, but the next best was an old RCA 5V4G. The 5V4G won't take the voltage and amps a 5AR4 will so you can't just pop one in untill you check your specs.
I think that part of the sound differences we heard was the amount of voltage drop, but the good ones went far beyond that. Sound stage, dynamics, bass, the sound of brushes on symbols, vocals, you name it were all changed by every tube and I think we tried close to 50. It gets a bit tiring listening to the same thing that many times but the only thing changed was the rectifier in the amp which was a flea watt at around 3 watts per channel, but the speakers were around 105 db SPL and 3 watts can hurt you with that. It was one of the best tube rolling sessions I have set in on and is a tube often overlooked by many guys with great systems.
All the rectifiers used were vintage and most were US made, the others all came out of Western European factories like Amperex or Mullard. The 5V4G was a great tube and they sell for low $$, at least in the US. I like the WWII JAN RCAs myself.
I have heard amps with the new globe rectifiers from China, but without rolling you can't tell how much the sound was influenced by them, though the owners swore by them.
This is my first post and I haven't really begun to go through the site. Is there a scale of lethality of the DACs and if so can you aim them? Not that I would.Yet.
Thatch