[morzh]

Also remember: there is no such thing as a noiseless fan.
Also fans in continuous operation tend to fail aftr a few years and they become noisy pretty quickly.

I would go for:

1. keeping the tube,
2. Slapping a piece of a heat insulator under the top (there's that nice one, with foil outside and the insulation inside).

And in those big floor radios the back is open so plenty of air inside.