I got those rca tubes in hazi talks about, and they are pretty dang sweet. I agree that the stock are a bit mid centric and not as balanced, I then threw in some Holland bugle boys and they were pretty sweet for treble and mid-range, but didn’t quite do what I wanted for bass (but I knew that going in). The RCA are well balanced and overall just a generally good upgrade without making many sacrifices imo. It balances out the sound, improves sweetness, a bit more natural and accurate presentation, and a bit more detail too. Soundstage also gets a bit more immersive. I don’t think it transforms the amp or anything, but it is a general all around improvement. I think the El tubes will most likely do the same but I haven’t tried those
Edit: also just realized this is the crack thread lol, I am using nos mullard cv4003 and nos mullard 6080 and it sounds great for my 1.1 w/ speedball