Dear @edgyhassle : " increase detail, realism and further tighten up the lower frequencies (and perhaps enhance), "
Horns speakers are unique in the sound Immediacy we listen against any other kind of speaker design.
Unfortunatelly horn speakers are not good enough at both frequency range extremes Your Belles goes down to 45hz with +,- 5db and to 17khz with same high level deviations .
You can have the kind of bass range you are looking for adding a couple of self powered and connected through its high pass crossover, with subs you will have additional benefits in the whole frequncy ranges not on ly in the bass range.
You can change your cartridge and this is an option too.
Regards and enjoy the MUSIC NOT DISTORTIONS,
R.