So Signaforce, first let me congratulate you on your PS audio purchase. You got a great product at a great price and will be happy with it for years to come.
in regards to tube rolling,I need to tell you that rolling is an “art” you see, tubes change the sound, sometimes greatly and sometimes very little. It’s all system dependent! What works best in your system might now work/sound as well in say my system. It comes down to trail and error! I went 5hrough a number of different tubes before I found something that improved the sound over 5he stock tubes and at 5he same time improved my listening quality. The best way for you to find out what might work best is to go to the PS Audio website and look at their forums. There are a number of threads on the preamp as well as tube rolling for the BHK specifically. I am not versed in tubes so the information I gleaned was very helpful.
wheather you got black or silver, you did good and well bought!