Sound Setup Question

I'm looking to combine a friends and my PA system for a gig this Friday. I'm fairly sure I know how to make it work but I wanted some feedback from anyone who has some experience with using different style components in a setup.

My main concern is the use of the Thru or Outputs on the Subs. Any advice would be appreciated.

Basic system:
S2 and Z2 going into Behringer 802 mixer http://www.behringer.com/EN/Products/802.aspx

Mixer Main outputs into inputs of powered 18" Sub http://www.behringer.com/EN/Products/B1800D-PRO.aspx

Outputs of 18" Sub into active 12" speakers http://www.guitarcenter.com/Electro-...77-i1751084.gc

Thru from 18" Sub to inputs of 12" Sub http://www.behringer.com/EN/Products/B1200D-PRO.aspx

Outputs of 12" Sub into powered amp then passive 12" speakers (pretty straight forward)

You will NOT need the 12" sub. It will only complicate things and will NOT help the sound quality.

How large is the space?
How large is the audience?
What is the genre of the music?

Adding the amp->passive 12" to the system adds a lot of complication...if that can be avoided, so much the better.

Well getting rid of the 12" sub and the two passive 12's cuts the system in half and idk if I want to do that.

Place has been bought and remodeled since I went last but its basically a bar with about 75'x75' with decently tall ceilings. Genre will be a lot of progressive house/trap/heavier bass stuff. Depending on what takes. And head count could be anywhere from 20-200.

Where does the complication come in with the amp/passive part of the setup? Its a pretty basic amp. http://www.behringer.com/EN/Products/A500.aspx And yes I realize everything is behringer. ha Cheap and has a 3 year warranty.

For a 5ksqft space, I would use two or four subs. Four subs would be preferred given the "bass heavy" content you are planning to use. Keep in mind that each doubling the number of subs will add +6dB of output AT MOST! Using a 18" and a 12" sub will add less than +6dB, and will muddy the resulting sound. Provided that you do not expect too much from a single sub, it will still be OK.

The complication comes from two point sources of sound that are producing the same content...but with different boxes. Getting the sound integrated will be difficult at best.

Place the single 18" sub, next to the wall, facing the wall, adjacent to the dance area. If you insist on using the 12" sub as well, place it on the opposite wall from the 18" sub. If you lack the cable to do that, leave the 12" at home.

The four tops can work. I would place the tops along a "long wall" evenly spaced.

Thanks for all of the info. I have quite a bit of cabling so I may bring the 12 and see what the situation is when I get there.

I'm still a bit lost on how to run the cabling. If the outputs from the mixer go into the first sub, then I have "Output" outs and "Thru" outs from the sub. I was planning on running the "Output" to the first pair of 12s and the "Thru"s to the second sub but that would require the cabling to get there and to get back to run the second set of 12s.

I suppose I could daisy chain the speakers... This is starting to be a headache.