I've got enormous improvement with tube amps on the bass. the music is more coherent than with the solid state amps. the bass is there also on low volume levels.

the amps have plenty of power and a low output impedance - four el519 per channel, so i dont know if single ended amp has a low enough output impedance to drive appropriately the Pi10 horns. If not the SE amp stays on the midrange horns and i would build some hybrid amps with tubes for the voltage amplification and a mosfet power follower to deliver the current.

i have a bunch of questions, your input would be great appreciated

how much distance do you need to the horns to get a coherent sound?
is nearfield listening enjoyable?
how big is your sweetspot? on my system there is a 1-person sweetspot.
could you send me the plans of your chopped bass horns to get a feeling how big they really are?

many thanks
peter