Hi Paul,
Happy New Year to you and yours as well.
Both the Maggies and your present speakers have the same nominal impedance, into which the reworked amp will be able to supply 300 watts. All three Maggies have specified sensitivities that are 5 db less than the specified sensitivity of your present speakers. The approximate maximum SPL at the listening position of 110 db that I calculated for your present speakers in my previous post did not take into account their powered woofers, which of course the Maggies don't have.
So it seems reasonable to me to simply subtract 5 db from the 110 db to derive an approximate estimate of the maximum SPL the revised amp would be able to generate with the Maggies at your listening position.
And 105 db at the listening position is certainly enough for most of us. Although I have a few classical symphonic recordings on labels such as Telarc, Sheffield Lab, and Reference Recordings which have been engineered with minimal or no dynamic compression, that can reach 100 to 105 db at my listening position on occasional brief dynamic peaks, while being listened to at average SPLs in the mid-70s. But recordings having such wide dynamic range are rarely encountered.
Best regards,
-- Al