15 inch speaker question for a Supro amp build

[Planobilly]

Hi

I have collected up most all the parts to build a S-6424 style Supro amp using El84s. 600VCT hammond PT #272FX and a Hammond1760H OT. I had in mind to bias the amp at about 18 watts.

I will only use the amp at home to record with.

I was considering using a 15"speaker.

Can someone comment on this idea and what brand of speaker?

Thanks,

Billy