you need to upgrade tubes in order to hear WA33 at its best
I'm not sure how true this really is.
The only tube I'd roll immediately on a WA33 is the rectifier, put at least an NOS RCA 5U4G (about $70) in it.
Better 2A3's will improve resolution and clarity to a point (and I have swapped mine), but the stock tubes aren't bad.
The input tubes aren't worth messing with IME.
The only "knock" I have on the WA33 is it isn't a SET amp, and that's more about preference.
Balanced tube amps cancel a lot of the 2nd harmonic distortion so you don't get a lot of mid range bloom with it.
It still sounds like a tube amp, but it's very much on the dryer side.
Those qualities are going to be broadly the same across all the variants, I'd like to hear an EE, but I'm happy with my standard version. I generally use it in preference to my original Cavalli Liquid Gold.
As an aside does anyone know what the gain switch actually does on the WA33, I asked Woo and got the following none answer
The way we implemented the HI and LO level output is very different from other amplifiers, it does not impact the sound quality.
I can guess at what that means, but I'd like confirmation.