I had been happy since I got Freya last week.
Stock tubes are not bad but it sound slightly veiled and lacking refinement .
Thus I recommend you to try Nos tube like Sylvania GTB or vt231.
All quad Sylvania GTB made in 1955 sounds neutral with somewhat gentle treble.
I had paid 200$ for quad from reliable Ebay dealer.
RCA gray tube in gain stage and Syl GTB in buffer stage give warm and lush sound.
Sylvania vt 231 which had been my favorite for last 2 years in Line Magnetic 508 int amp give more transparent and clear details when used in gain stage.
Out of curiosity I had gone to all quad stock tubes.
I had run demagnetizaiton tracks twice ( 6min each) and started listening to Eva Cassidy's "Autumn Leaves, Songbird" , "The Trinity Session" by Cowboy Junky and Trittico by Fennel for classical music.
I had expected somewhat etched or bright sound out of JJ stock tubes.
Wow Freya with stock JJ tube sounds very dynamic with good details.
Compared with Nos tubes, it is slightly veiled and lacking refinement, but it is still quite listenable.
It will improve after break in.