Modify tube amp or upgrade to NOS tubes


I am reasonably new to integrated tube amps, and have played around some with switching out the stock tubes for some other current production tubes - SED & JJ KT88s; Tung Sol 6sn7 & 6sl7, Grove Tube EL34 to get a sense of what differences in the music there might be. Putting all else aside - what makes more sense to those of you with more experience with tube amps if I want to go a next step - have amp upgrades e.g. resistors, capacitors, power supply; or get NOS tubes?

Thanks for any insights
facten
You will wind up with NOS tubes anyway, so go for them first. I recommend cryoed tubes. Google tubeman.com
I would be inclined to go the NOS route for the preamp tubes and current production for the power tubes. I have a Prima Luna Prologue 2 integrated amp and a Prima Luna Prologue 5 power amp. I have gone with NOS for the 12AX7 and 12AU7 (Mullard & Sylvania) and have stayed with new production Electro Harmonix for the EL34 & 6550. I discovered two things along the way:

- I prefer the sound of the EL34 & 6550 to KT88 (sounds smoother to my ears)
- EH lasted longer than JJ and SED Winged C in my Prima Lunas.

Regards, Rich
Think of it this way. NOS tubes are going up in value and modifying a piece will reduce it's value