You will hear a more noticeable improvement by changing out the ECC82 (12AU7) and ECC83 (12AX7) tubes than the EL84.
You’ll have a hard time finding someone else with your identical system. Someone with the same amp and tubes will sound completely different to yours. And if you’re using NOS tubes, there is a wide variation between batches of the same tube. All you can do is listen to the tube in your system and make a determination if you like it or not. That’s the maddening part of tube rolling - your mileage will always vary!
For ECC83/12AX7, my favourites are:Shuguang Custom 12AX7 LS
Mazda Chrome Plate ECC83 (getting pricey now)
Telefunken ECC803S (very hard to find now, v. expensive with lots of fakes out there)
For ECC82/12AU7:Psvane 12AU7-TII
Amperex BugleBoy 7316
GE Triple Mica Blackplate 5814A
Telefunken ECC802S (same caveat as the 803S’)