Is a SUT needed?

Nandric:
I'm not clear, on what aspects makes one tube superior to another.  You read about NOS (new old stock) being the best.  It would seem with technology being so much better in our modern times, a superior new stock tube could be manufactured.  My guess is the market isn't strong enough.  Tube suppliers, such as Andy's Vintage Tubes, measure and match tubes, based on their measurements.

@handymann 

Glad to hear my suggestion helped with your problem. I assume you just replaced the V1 and V2 position tubes left and right. Those are most sensitive to noise issues.

jperry:  I replaced all four

Is an SUT needed? No but IMO (only) I find an SUT into a MM stage gives me superior results.Better dynamics more detail and a more natural presentation. I've tried many SUT's and have found the Kondo SFz step-up the best until recently.  I have recently tried tbe SA Labs SUT from Russia to now have outperformed my beloved Kondo unit, and at a less expensive alternative. 

sksos1:
Once I replaced my "new" tubes from my upgrade from a standard Rhea to a Signature Rhea, with  very low noise matched tubes, my noise floor is as quiet as a tubed preamp can be-almost.  I chose the the RCA quad matched 12AX7's from Andy, at Glenn Buckley's from Aesthetix   suggestion.  I would have thought the upgrade would have provided these, but it did not.  I have plenty of gain, as I set my input to "62."  any higher and I get over modulation.  The cost was around $300.  I could have spent more for even better tubes, but you have to place a limit somewhere.  I may upgrade my tubes from here-hard to say at this point.  No matter how much one invests, there's always something better.  I think I'm looking for the perfect system and on my budget, it just ain't gonna happen.  I'm considering different cartridges, as well as more room treatment.  Don't misunderstand-my sound is absolutely great, but there's always something better.  I'm pleased with all my hardware.  Looking for that unicorn.