Metal or Carbon Resistors - Which is better?

Alex, 

You raised good points about 300B driver stage design.  Unfortunately, many utilize 12AX7 drivers and no interstage transformers.  Hence, it remains the case that many 300B amps are a bit polite, dynamically speaking, but 300B amps are favored because of their glorious midrange.  

A 300B amplifier can sound dynamic if it has a properly designed driver circuit. The 300B tube is much more difficult to drive than 2a3, 45 and px25.
@alexberger 

Agreed with your assessment. A 300B amp can sound very dynamic, but it all comes down to the driver circuit design (that’s where my last amp failed to deliver despite of more than one revision). The 300B requires significantly more drive than 2A3, 45, or even PX25, and if the circuit can’t deliver sufficient voltage swing with low distortion, the amp can end up sounding soft, distorted or underwhelming. 

A well-designed driver stage especially one with strong current delivery and proper impedance matching makes a world of difference. I’ve heard 300B amps with properly executed driver circuits that were anything but polite…fast, vivid, and emotionally gripping.

I wonder if anyone heard this amp, 

https://fezzaudio.com/en/produkt/fezz-mira-ceti-300b-evolution/

When Steve McCormack helped me remove the volume control from the signal path in my SMc Audio preamp, I ended up choosing Audio Note 2W Silver Non-Magnetic Tantalum Film resistors to install in place of the stepped attenuator.  Sounds great, no regrets.