I've heard both during my time at CanJam 2022 Socal. From what I recall, WA33 is more technical and less rolled-off in the treble than the Envy. I believe, I used the low-impedance setting in the WA33 and medium impedance with the Envy with the Suvara pairing. The Envy has a more "expressive" mids than the WA33, and both have that concert-hall imaging that is the trademark of tube amp.

When it comes to tube amps, the best breed would be the "Directly Heated Triode" Single Ended Tube amp (WA23, WA5 LE, Feliks Envy, Eddie Current amps) or Fully Balanced Push-Pull directly heated triode amp (WA33). They differ in output power as well as output transformers and as such will react differently with the same headphones. Only way to tell is to actually demo them with your headphone of choosing.

> Also is every input hole like adding gain on a standard amp?

Nope. If you use two of the headphone amp outs at the same time, you increase the load of the amp (on the output transformer specifically) and depending on the sensitivity of the headphones used, one will sound louder or quieter than the other