I know you might be a purist but trying something cheap anyway might get you excited. Get an electrolytic 1.5mf cap, a 1.5 ohm resistor and a 220 ohm resistor all in parallel. And connect to the FR drivers and hear what happens. They will keep up with any tweeter! The 220 ohm (for some reason) has a top end boost that is at another level. Don't ask me how, just hear it. And electrolytic caps sound better on FR drivers than ceramics. Less brittle and more silky in sound (I reckon).
I also have some FR + woofer speakers (that I heard yours on). I design and build speakers as a hobby. I have two concepts that I might sell examples of. One with an 8" coaxial driver + woofer and another with a 5" FR driver + woofer. Both designs have a conventional box (but that's where the similarity ends). They are completely different in acoustic treatment to your speakers, not open baffle or conventional closed driver mounted either. It's semi open and semi dipole FR driver mounting over the acoustically treated speaker hole (witch also doubles as the woofer bass vent). Imagine holding a FR driver over a bass vent (that is basically what it is). A point source bass vent with the FR driver. And with a conventional woofer mounting but on the bottom panel facing straight down onto the floor (with breathing space under). The speaker has a semi open point source sound with a vague woofer source sound.
