IMO the tube upgrades are a must specially the 300B and rectifiers. The one I audition before ordering mine had Sophia with RCA drivers and sounded very good. I am running EML 300B, Tugnsol 6F8G and USFA 596 and IMO sound great.
I did go all the way with parts upgrades, sockets upgrade and even send Jack the wire for internal wiring (OCC Copper Neotech) and Cards Eutectic solder. Later I upgraded the umbilical cord to one made out of the same Neotech OCC Copper chassis wire.
I love my WA5-LE.
This is a serious definition of "Hobby" how cool is it that the builder will accomodate the buyer with specific changes of even internal wire....I love this stuff!