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.
128x128rvpiano
lowerider57,

You’re absolutely right,  As I mentioned, the tests were only preliminary.
I haven’t given the Amperex enough time yet to burn in yet.
Im going to leave them in for a while to give a more thorough evaluation.
Thanks to all of you that gave advice about NOS tubes.
They make a HUGE  difference in the sound of my set.
I sold the Belles. They were definitely not compatible and were not powerful enough to drive my system.
The NuForce are much stronger, and they sound fabulous.