Actually, if they do not have a sub, then they should also run the L&R speakers as full range. Either way, if you have external subs, then that is where the crossover should come into play, not between the top and bottom sections of the mains. Lots of folks with issues trying to use the bass modules as subwoofers. Just try it both ways and see what works best. Nothing to lose.That is making an assumption that the person has external subwoofers. Additionally, why would anyone buy full range speakers only to cross them over to external subs? Seems like an odd choice.
If you have Tritons with built in subs and no external subs, the LFE channel should be connected to your Tritons with a subwoofer cable.