Thanks for the links. I read through all three of them and found them very informative.
I think that budget considerations point to the Three Pi with the Eminence Delta 12LF, but I'd like your advice, given the following added information:
[1] I do not wish to use subwoofer(s).
[2] I will be using 7 cu ft speaker cabinets [home built in the 1950s].
[3] I have always preferred the effortlessness of 15-in woofers, but the Eminence Omega Pro 15 modeled by WinISD in a 7 cu ft box is down 3 dB at about 41 Hz, whereas the Delta 12LF appears to go down to 27 Hz...BUT, I don't know if it can really deliver down there.
Can you see a straightforward choice for my project?