What components would you be using them in?
What are you presently using?
What about their present sound do you want to change? That is what are you trying to improve?
Is your present problem one of clarity (resolution), tonal (dull or bright), noise, etc.
Consider that you might get more specific responses if you posted a new thread asking for help getting new production tubes for you XXXX component, including the above information in your thread. There simply isn't one tube that fits all circumstances.
