I am not a BIG fan of using a subwoofer for music but the REL stuff is about as good as it gets in my opinion. A Rel Strata Used I believe will run you $850-$950 used here on Audiogon. I know a little out of your budget but I would dare to say well worth the price of admission.
You might want to also consider just upgrading to a Floorstanding Monitor. Good Luck!
Chris
You might want to also consider just upgrading to a Floorstanding Monitor. Good Luck!
Chris