Hi Arolf,

I'm sorry I didn't notice this post sooner... like when you posted it!  

If you can accommodate a symmetrical pair of speakers in the front of the sanctuary either standing on the stage or possibly hung depending on the room shape... consider building a pair of Imperial horns.  These are large rear-loaded folded horns that can be built into the wall, or free standing or hung.  They typically use a single 15 inch woofer, a midrange horn and high frequency horn, or in some cases just a good coaxial 15 inch driver can be used which makes life simple.  These cabinets will easily hit 22 Hz and don't need much power.  It would even be possible to drive them with tube amplifiers which would no doubt make God smile.

Here is the link https://www.decware.com/imperial.htm

Steve