Re: Rather than like buying a BMW
"Most Radios only need four or five, [...]"
The constraint on any analogue audio amplification is staying in the linear part of a device's response curve over the whole dynamic range - yet with a reasonable signal to noise ratio.
A classic decent superhet radio needed an RF pre-amp, an oscillator, a frequency mixer, two IF stages, a detector, an audio amp, and an output amp. Double up the audio if it is stereo. Throw in another device for full wave AC/DC power. Some of those functions were doubled up into one valve envelope. You could even throw in another valve as a "magic eye" tuning indicator.