JJ 300 B tubes or others ?

Pretty much any tube that replaces the JJ will be an improvement. I was very unimpressed with JJ300B tubes. The Shuguang BT represent the best value for the $ right now and are well made, unlike the JJ.

Rebbi,
At your stated price point you won't do better than the Black Treasure tubes(BT) IMO. When the BT was first available for sale they were 600.00 per pair from Grant Fidelity. Given their performance at that time(2009) they were worth it relative to the 300b market then. They sound very good and are quite reliable with very good construction. The JJ is in a lower tier.
Charles.

Charles and everyone,
Nice to have a clear consensus. I'm upgrading the rectifier and remaining signal tubes in my Kit 1. The 300 B's will be next. Nice to have a path mapped out.
Thanks again!
By the way, seems that Grant Fidelity is out of the tube business... at least I cannot find a link to tubes on their site. Happy to be corrected if I'm mistaken.

There is a hyperlink on the Grant Fidelity home page for tubes.

I believe that PartsConnexion is selling (perhaps bought) Grant Fidelity's stock of tubes. Their recent advertising is cut and pasted from Grant Fidelity. Or check w member Trelja; I believe he also sells the BTs.