Which tubes to spend the most money on in a PV-5?

I have a CJ PV-5, but don't really understand the circuit. The tube layout is here:
http://www.conradjohnson.com/It_just_sounds_right/a-PV5.html

If I am going to put expensive tubes in the most critical slots, which positions/tubes are the most critical to the sound?

Between Telefunken, Amperex, RCA, GE, Mullard, and Sylvannia, are there preferences to get the best sound for any particular position?

Thanks for your help....

Jim