I have always loved tubes and have built some breadboard rig just for fun. Now as an audiophile of the underground single ended set. One can buy ANY part for these great sounding amps.
Kits abound and tubes hold a big market to good sound now.
Especially in Japan which is in love with the Western Electric 205-D tennis ball tube at 1.5 watts in SE use. Their horn systems shine in multi tube amp systems. My system uses horn bass with altec driver and 805B multi cell mid-tweet using 211 SE transformer coupled monoblock at 25watts. Enclosed are some pic of gear made by me that might be of interest to you. 400watts used on 160 and 80mtrs.