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 like the 5814a variant of the RCA Blackplate. It is more dynamic than the 12au7. The Cleartops are good if you like extended highs.

Re... the Blackplate 12AU7, the older the better. Early 1950s, low noise is best for the classic tube sound.
I would imagine RCA Cleartops would work well in a CJ due to their airy high-end.
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 .