Rhea and tube noise....????

I have auditioned the new Aesthetix Rhea (early version) and was pleased with it. I only had it in operation for a few days. However, I am getting reports for users that the unit does exhibit some tube noise. The suggested remedy for this is NOS tubes, which could be costly.

Here are my questions: Any Aesthetix Rhea users out there have experienced tube noise with their unit??? If so, what was the solution??

Have any of you replaced the tubes with NOS, and if so....which ones....??...and at what cost???

Thanks again everyone!!