I think this plan is probably better for you.



Sit at the wall facing the smaller wall, where u can place the front speakers better. Surround can be placed far away from your sofa, about 9 ft above the floor, and facing towards the centre. that way I think u have better room to play with your equipment.

I think it can be pretty tough to solve your problem. I was even thinking of putting the tv against the right sided wall, exact opposite to your original design. But then your mother will hate the tV facing the door thing.

Not much solution I think.