tube recommendation please

I am brand new to tubes and need some advice. I have a PrimaLuna Prologue three which use two 5AR4, two 12AX7, and two 12au7. I listen to female vocal mainly, hopefully I can get bigger sound stage, and smooth and warm vocal.

I start off with the 12ax7 and ordered a pair of Tungsram produced in 1967. I am also planning to get a pair of 1960's Amperex, but I am waiting for some more reasonably priced.

My question is .. what should I get next? Should I upgrade the 5AR4 or the 12AU7 next? and is there any suggestion on those tubes?