To clarify a couple of things: I am not proposing a "bookshelf" system but am looking at two systems, one a stand mount monitor (9"w X 20" tall?) and the other a small floor stander.
Cool! Thanks for clearing it up.
Several of you have echoed my sentiment that it is best to use a subwoofer for room filling bass extension than compromise the main system. Spot on!
Fair, but I would caution about taking that notion to the extent that some have mentioned earlier - 80Hz, 100Hz, 120Hz... because in that ballpark of low frequency extension limitation, particularly if you are talking about a premium (priced) product, I think you'd be hard pressed to find any who wouldn't say that for a speaker system
using the proposed speaker a subwoofer is no longer optional but a basic requirement. If a subwoofer becomes all but required to be satisfactory, the total system
cost now needs to include both what are supposed to be a more entry-point taste of Daedalus and, what, a pair of BOW at the minimum? $5K becomes $10-15K real quick, and then you're back in the ballpark of just going with a Muse (or Muse Studio) as your entry point and being further ahead.
That's why I thought with the efficiency you mentioned targeting, the 50Hz extension target was a very intriguing twist. For what little it is worth, I've swapped out sealed MTM 6.5" 2-ways rolling off at 60Hz for ported TM 6.5" 2-ways (using the same tweeters and midrange drivers) that roll off in the mid-low 50s specifically because the ported speakers could enjoyably be played alone with most of my music, where the sealed speakers just couldn't get it done. It may sound silly (and I know there is probably a line of people who will argue the chestnuts about imperceptible localization below 80Hz, etc.) but I feel not only is that frequency range key to the exercise but how that frequency range is handled - particularly if that is going to be the bottom - really matters.
Ultimately, my post is to say when planning this idea, if the idea is for the speakers to be a starting off point that a customer could build upon and grow over time, making sure a customer could be happy with say 90% of their music with just the two speakers they get to start with until subs and such get in to the budget is important. If they are meant as basically a trade-up demo, or as really part of a turn-key satellite/sub swarm solution from the onset, where and how the low end is handled becomes a lot more flexible, but you'll be losing the real $5K cost of entry if that was a goal.