Rec a 300B for Wavelength Cardinal Monoblocks

I am looking for recommendations for 300B tube choices for my Wavelength Cardinal Monoblock amps. My speakers are the Auditorium-23 Solovox and the preamp is a Shindo Masseto. I know that I will eventually get a Shindo amplifier, but for now I am intrigued by the prospect of learning how much better the Cardinals can sound with other tubes. Also, there is the very real possibility that I would keep the Cardinals and alternate them with the future Shindo amp, assuming the Shindo amp does not use 300B's. Thanks in advance for all guidance!
Best Regards,
Steven