Definitely get the GE 6BZ7s, they're really good! in fact, once they burn in (which can take some time, give them at least 50 hours) I could see myself using them indefinitely, if I didn't already have tubes waiting to try.
The Lyr tube rolling thread is a WEALTH of information. Be sure to check it out.
Forgive me i'm somewhat confused should I try the GE 6BZ7 stock option or spring for the 20 dollar version? thanks