Subwoofers and Seating Position for Klipsch Forte iv's

Hi All, 

I am trying understand seating position and subwoofer size/power requirements.

My room is 35 X 15 x 8 = 4200 cubic feet. The room setup (music only and no HT) is such that my main speakers are on one end of the 35 foot length and my seating position is about 11 feet from the speakers, such that half of the 35 foot length is behind me. There is nothing obstructing the whole 35 foot length except the seating position.

My thought is that I would obtain two subwoofers and start with them on the same end of the room as the main speakers. I realize room modes may impact subwoofer positions, but I am hallucinating that only one of the subwoofers would  ever come further into the room than on either side of the listening position and not end up at the other end of the 35 foot length.

So I am imagining that I am really trying to energize just the half of the room that is closest to the main speakers.

My speakers are Klipsch Forte iv's connected to a Don Sachs preamp and then to a variety of amps between 25 and 100 wpc per channel (Van Alstine, FW F7, DS  Kootenay, and Quicksilver horn monos). The Fortes are specified as handling 100 wpc continuous at 112 decibels. 

I used to run Thiel CS5i's in this same space and a McCormack DNA 500 would provide "in my chest" bass response when I cranked it.

Been looking at HSU (15 inch & 450 watts, SVS (13 inch & 800 watts), and Rhythmic (12 inch & 400 watts) as these manufacturers seem to garner good reviews for being musical without going beyond the $900 to $1200 per sub range.

Any advice or suggestions would be appreciated.

Thanks for listening,

Dsper

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