Not be disrespectful or anything towards Forest Man
BUT Shoving lo-mid range receiver into tight budget with very specific demands seems, to say at least, unbalanced. Not to mention monsterman specifically mention he rather not get it now, and system to be easily upgradable.
I agree with agarwalro - I double checked and - my bad: active behringers don't work in passive mode, which I assumed they would for some reason
Pair of Passive 2030p's (or other large bookshelfs), A500 amp and sub(s) of your choice seems to be they to go.
Edit:
I did some research about Dayton Audio subs, but Its a bit hard to believe - good sub for $120 ?
Audioholics reviewed much more expensive [$800 if im not mistaken] Dayton sub before, yet to find it near perfect... Do it makes sub from same maker, which cost 6 times less cost nearly as good as $800 one??