Just FWIW, 'Efficient Full Range Speakers' describes a class of speakers that use a single driver running full range with no crossover. Examples are Lowther and PHY. But it sounds like this is not what you are talking about...
Audiokinesis makes and has made speakers that might be what you are looking for. Not sure about the price, but if you can find a set used they could fit the bill nicely. His speakers are musical in the ways you are asking about and they are easy to drive. Good Luck!
Audiokinesis makes and has made speakers that might be what you are looking for. Not sure about the price, but if you can find a set used they could fit the bill nicely. His speakers are musical in the ways you are asking about and they are easy to drive. Good Luck!