hi dusty,
i wonder who tol' ya to come here? hmmm...
re: subs w/monitors, that's how i run my present rig. even tho i lust after big full-range speakers, i willstill keep my subwoofer system if/when the big monitors ever show up. imo, it allows the main speaks to perform better.
but, as you said, good x-over is crucial. as far as subs w/nice x-overs, there are none that i'm aware of.

at least none that i could afford. i would strongly recommend passive subs w/outboard active x-overs & amplification. while it may seem intimidating at 1st, to set up a system in this manner, in the long run, it's far more flexible, & you will end up w/far better subs *and* electronics, at any price-point, if you do subwoofing in this manner. i am really happy w/my marchand xm-9LL active x-over & a pair of vmps larger subs. pick any decent used solid-state amp(s) to match. if you spend four times as much $$$ on powered subs, you *might* get close to the performance...
ymmv,
doug s.