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.
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.
Thanks for the info.  If the RCA’s don’t work out, I’ll return them and try 5814’s
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