Radio experts help needed picking radio

I am looking at a Zenith 805 cathedral.  Is this a good reliable radio to get if it's my only antique radio?  What would the value be on a good working one?

I want it to be portable and have good sound quality so a room full of people can hear it well.  It's not the prettiest cathedral, but I want it to perform well also.  I am also looking at a Crosley 168, maybe a Philco or Atwater Kent.  If there are even better options, please share.

BTW, what is that fourth knob for?

Thanks

Figured the fourth knob out. Selector between AM, SW and a tone.