A tube rectifier has a major advantage, built-in slow warmup. But it has a lot of disadvantages--wasting power, needing a separate filament winding, causing massive destruction if it develops gas, etc.Cheap diodes have slew-rate problems which can increase the noise floor in the amp. I'd use FREDs, and a time delay switch or standby switch. And recommend you precede each diode with a 100-ohm 5w resistor to reduce the turn-on surge. That simple trick can increase reliability of the power supply considerably.