300 B Shuguang Black Bottle tubes

Just got them from Canada (from NA distributor) and put as a replacement to my Audion Silver Night 300 B. I used to have 300 B (Hot Rods marked), I think they were codenamed as Golden Dragons (correct me if I am wrong), had to replace them recently, I got what I could get in Russia - Svetlana 300 B ones. Svetlana by all means not bad tubes (I thought way better than the ones I used which came with amp), but Black Bottles are just another league way up from what I heard. Suddenly bass became very articulated (used to be rather boomy), soundstage is a huge improvement at all.

They are in burn in process at the moment (as I read they really start signing after 300 hours), I am wondering whether anyone did have an experience with them and whether it is as much positive as mine (very addictive tubes!!!!).

Anyone?