Hi,I just ordered my Crack kit with SB few days ago and i'am looking for any reasonable price upgrade tubes.These are the Tubes i have RCA 6AS7G's,Raytheon 6AS7G's,Sylvania 6AS7G's,Chatham 6AS7G's,RCA,Sylvania,GE 6080's,JJ,EH,Rogers 12AU7's and Various makers of 6SN7's.Can i use the 6SN7 with the Crack?Thank You!