NOS 2A3 or Sophia 300b 2.5v in Consonance Cyber30?

I picked up an Opera Conance Cyber 30 2A3 SET amp to use as a headphone amp. Aside from a very slight hum (that is not noticeable when music is playing) it sounds nice with my Grado GS1000i headphones. I am currently using an RCA ECC83 driver and Sovtek 2A3's in it but would like to try upgrading the power tubes. The two tubes I have been looking at mostly are the RCA double black plate and the Sophia Electric Princess 300b 2.5V. I am new to this so I would welcome any input or suggestions from you experts.