Tube choice makes a big big difference in my amplifier circuit; differences in input tubes, power tubes and rectifiers really are quite apparent. I've done some judicious shopping and have found that RCA rectifiers and Siemens input tubes are the best combination for me, and compared to the Svetlana and Ruby (Chinese) stock tubes they are no comparison: the NOS are clearly superior and I won't do without them. It really surprised me what a difference rectifier tube rolling has made; the partnership between a rectifier and an input tube is quite important and I've found a really great one in Siemens 6922 and RCA 5V4. The Seimens 6922 also work really well in my Dynaco CD player, and I have a pair of Mullards that also work excellently.
I've looked around and really have found bargains for the NOS tubes I prefer and have a supply that will last me a long time.
For output tubes, my amp uses the Svetlana SV83 which is a newly developed tube with no real direct replacements in vintage gear. EL84s work, electrically, but the SV83 yields more power, and has a wider bandwidth, it's really no contest. The treble is much better with the SV83, extended and open, and the midrange is very open too; EL84s sound somewhat midrangey and compressed in comparison.
So my amp is split between new production Svetlanas and NOS stock tubes. And I'm ecstatically happy with the situation.
In your amp I would recommend playing about with NOS power tubes. I find that EL84s by Mullard and Tesla are better than Russian and Chinese tubes, in three different tube amps I've owned. And I also believe that you can really enjoy differences in input tubes and rectifier tubes as well. I would think with your attention to detail in your system that you would explore this avenue to improve and tailor the sound, and enjoy the adventure.