GTP, welcome. Yes, the crossover to the M2s should be no lower than 80Hz and possibly 90Hz(if available)or 100Hz would be better. Another thing to consider is whether the "forcefulness" in the old Bostons was due to an inaccurate boost in the upper bass area, while the M2s are more accurately reproducing what's actually on the recording.

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Enjoy the music, not the equipment.