Pi center channel and sub


Grettings,
I'm new to AV setups and I will still listen to just the 4Pi's and foreplay paramour combination for music BUT...
I'm looking for suggestions for a center channel and subwoofer to go with the Theater 4Pi front and studio 2Pi rears I'm building.
I want to use the same horn as the 4Pi in the center but my space is at a premium (I really have no idea how I'm going to fit all this in my living room and not freakout my wife) so I will need to use something like 2 6" woofers horizontaly. Alpha 6 comes to mind, but how do I deal with the impedence issue? Run the woofers in series 16 ohm?
Any other drivers that would allow me to use 5 low powered set amps like paramours in this config?
I have a NHT 1259 250watt subwoofer but it doesn't seem right to use a 12" sub with 15" mains, I was thinking of more like a 15-18" driver in a small box with some EQ to cover the effects.
Any Ideas would be welcome.


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