Question for tube aficionados

I have a vintage Conrad-Johnson PV 11 preamp.
 I’ve always re-tubed it  with the cheapest tubes from Tube Depot (e.g. Electro-Harmonix 12AU7 and 12AX7, Sovtek 5751 and the like.). I’ve been very happy with the sound.
 My question is:
 Would it be worthwhile to spend more money on more exotic tubes?
  Would there be any appreciable difference in the sound?
 I’m powering the system with NuForce Reference 9 V3 monoblocks.
I’m looking forward to your listening impressions of the RCA tubes in the CJ preamplifier. Curious to know how much of a difference you hear compared to your current tubes. I believe this is a good terms of venturing into the realm of recommended NOS tube rolling. The cost of the RCA tubes seem very reasonable.  Good luck.
For Classical music I use 5814 and 5751 for 12Ax7 subs .
IMO opinion RCA cleartops are too bright on strings , maybe OK
in warm pre  but 5814 are always more musical to my hears .
What I can add is the best 12AU7 are 7316.
And the best of these are the Amperex Bugle Boys...

A lot of 5814s around- be careful- many are not as good as even the Chinese 12AU7s (which are really fairly competent).
The 5814s and 7316s are better grade 12AU7s.

I go back and forth with the fantastic Amperex 7316s, and the equally fun CBS 5814As. These are my faves.