Awkward room treatment/New monitors

[Unknown Artist]

I'm moving into a new place. I have been using
headphones forever, but I have the ability to use monitors now, so I've
decided to go with the Yamaha HS8s and the HS8S sub, as I mostly make
bassy music, and have an understanding that they have a very flat
response and good quality for the price range.
The problem is, i'm worried about acoustically treating the
room. The room is pretty big, and akward shaped. I will be sharing the
room with my wife, so i'll only be making noise when she is at work and I
am not, and it's going to be tough to convince her to let me hang a
bunch of acoustic treatment stuff, as it will ruin her decor(Women!
...Sheesh).
I have two main concerns..
Will I need the 8" cones, seeing as how I'm getting a sub? Should I
go with the cheaper 5 or 6.5 inch ones, or is there a benefit to using
the 8s seeing as how the low end will mostly be taken care of by the
sub?
My other concern is about the room itself, it's a "U" shape with a
bathroom against the middle of one wall. She wants to stick me in a
corner, obviously. it's about 30 feet wide, with an A frame ceiling that
is like 4' high on the sides and 15' high in the middle. I have heard
that bigger rooms need less treatment, and she wouldn't like the look of
it, unless it's vitally important. I was wondering if anyone had any
input about either the subs or the room itself.
I've uploaded a beautiful artistic representation of the room at imgur dot com slash NSs0gwW. Thanks for any and all input guys!

 

[Innovine]

Awkward rooms are best, square ones are worst. The sloping ceiling is a big plus, as is the stairs and open side. You didn't mention what its all made of.

For pretty stuff, I would recommend making your own panels and bass traps. Make a 10" thick panel of dense insulation rockwool in a wooden frame, covered with a fabric. You can upload graphics to spoonflower.com and get it printed onto textile. Mount the panel about 10" from the wall too, that air gap is often overlooked yet works very well. Even 5" of panel and gap is good. You should also probably try figure out whats wrong in your room before you try fixing it.

 

[Mania]

If you have a sub, you only needs 5"s

 

[Niwun]

You should also probably try figure out whats wrong in your room before you try fixing it.

Best advice here, a lot of panelling on the walls without knowing what's wrong with the room will just dull the high frequency response.