Hi rwpollock,
I tend to agree with charles 1 dad about some trade offs when changing hifi components.
If it is any help, I recently changed from monoblock amplifiers using EL34 (Gold Lion KT77 output tubes) which I owned fror 24 years. No - Í certainly don't change my hifi very often !
I changed to a pair of Melody 300B-1 monblocks and quickly rolled the Shuagang tubes to Mullard 5AR4 (rectifiers) Sylvania 6SN7GTB (driver/input tubes) and Emission Labs 300B-XLS (output tubes) and this made a big difference to the final sound quality. Even the change of rectifier tube added more "body" to the sound with each tube change providing an improvement in sound quality. This exercise in tube rolling cost around A$2,000, but I definitely think it was worth the investment.
The 300B SET monblocks were definitely a step up from my original EL34 amps in all respects of sound quality. I understand that the EL84 gives a similar sound to the EL34, but different circuit designs and component qualities makes any comparisions difficult.
I was extremely lucky to get an in-home demo on my Nenuphar Minis for two weeks (thanks Craig @ Audioheaven*, Melbourne) before I finally replaced my Sonus Faber Grand Pianos (the original version) of 25 years.
[Thanks rick2000 - you reminded me to give Audioheaven a plug for their excellent customer service].
Unfortunately, in the world of hifi, a home demo with your equipment, in a controlled environment, with enough time to assess what you like, is the only way to be certain if your are really upgrading, going sideways "going in another direction" or even going backward in your new hifi purchase.