There is no perfect room as each room has it's own issues due to it's size. You would want your mains to be as far apart as you are sitting away from them and you do want ample room to have space to the side and behind the seating area for surround speaker envelopment, the more space the better suited direct radiating speakers will be, the closer confines allows the QS series to shine, at least with my experiences.
The center speaker, if it is a horizontal design, is best near ear level but I have also had very good luck at any postion above or below the screen with the speaker angled down or up towards the seating postion.
It sounds to me like your room should work quite well, I would just watch that first reflection point from the side walls as the mains will be quite close to them.
Good advice!
