A worthwhile goal and makes sense since you already have subs.
A decent sealed 2-way design should reach 60 Hz (with a 6 inch woofer) which should easily integrate with multiple subs. Yes, large cabinets, large drivers, and complex crossovers are more expensive. The inherent complexity, size, and expense of a 3-way versus a 2-way to over work the woofer, gain extra bass, and/or output is a matter of trade-offs.
One of more promising smaller 3-way designs is the BMR Philharmonitor, which Salk can build for you. It uses a ribbon tweeter, Balance Mode Radiator (BMR) midrange, and 7 inch woofer and can reach 40 Hz (overkill for you). It comes from Salk's crossover designer, Dennis Murphy. Prices start at $1350/pair. Unfortunately it is a ported design and only 85 dB/w/m efficient (quite low).
Another option would be Omega single driver Super 3i monitors. Stated response down to 55 Hz, 94 dB/w/m efficient, starting at $695/pair, many different veneering options and Louis does good work. Lots of support here at Audio Circle, but again ported.