Thanks very much, Wayne!
So I may need to reconsider placing the subs as above written. I could also place the subs diagonally.
My room will be rectangular, roughly 9.8 x 18.2 feet.
The distance from my sitting area to the front wall will be approx. 12.3 feet.
This means I could place one sub diagonally behind me in the corner of the room and the the other sub equidistant diagonally in front of me.
Basically I could choose from any of the four options on the audioholics page named "Subwoofer Connection Guide For A Multi Subwoofer System" (I can't post the link yet). In your own experience, which do you think is best?
Ah, and about the rear surround speaker, you are saying dipoles or bipoles are not good, so I should better choose a monopole speaker?