What I'd like to make is a pair of "attractive" "compact" passive tops capable of 115 to 120dB average, measured whole-space, and a 65hz F3. Maybe 70, but 65hz would be nicer. That's the aspiration, anyway. I'll be honest, I don't even know if that's possible. I know some commercial options claim even better than that. Even if it's literally possible, I don't know if I can make a good system do that. I guess the only thing to do is focus on the low-end frequency response I want, then make sure I don't have xmax problems.

Tried modeling a few pro woofers here on PE and xmax issues were apparent with the first few I tried. Gave up on 6" woofers. I did find an 8" LaVoce WAF082.00 that seems to get me there, if WinISD is to be believed. With a pair of them in a 1.2cu ft. box tuned to 72hz, I get an F3 close to 65hz, F6 close to 60, F10 around 55hz. No real excursion issues at full or peak power. I hit xmax at 60hz at peak power. At peak power, WinISD calculates 121-122 dB max SPL.

Just to see how that is compared to commercial options I looked at the specs on the PreSonus 328ai and QSC K8.2

328ai claims 133dB peak maximum, 54hz F10, 59hz F6
K8.2 claims 128dB peak maximum, "Frequency Range" 55Hz-20k, and Frequency Response 59Hz-20k

Those are both powered, and there's some DSP shenanigans. I assume the low-end gets limited at peak levels. But how does "peak maximum" compare to WinISD max SPL?

So I guess the next steps are make a driver measurement jig, buy the drivers, measure them, then use speakerworkshop or vituixCAD to make a crossover?