Nothing wrong with building a system around a particular amp, especially if there is a specific tube you like the sound of. Low powered tube amps have limitations, as has been stated above, with speaker choices. More often than not, they require bigger boxes. I write this as I’m listening to a type 45 amp, driving a pair of 6’ tall double backloaded horns using a full range driver. Not to everyone’s taste, but I find the listening experts be quite enjoyable.
Good luck with your search!