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.
Thanks for the info.  If the RCA’s don’t work out, I’ll return them and try 5814’s
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I never had good luck with that variant. They often sounded harsh and microphonic. So I'm not the best person to ask...
I contacted Conrad-Johnson.  They sell a complete set of recommended tubes for the PV 11 for $310.
I wonder if I should go in this direction.