I want to add something to this topic here.
Sure it is important to treat a room. Yet NOTHING replaces proper acoustical design... there's no way a small room with any amount of DYI or any acoustical product (even RPG !) will sound like a professional control room.
People in this forum only think about frequency response and forget other factors such as time response, psychoacoustics, background noise etc....
Some more information on this online article I wrote
here
And yes, I do consultancy for both home and professional studios and I also sell acoustical products so I have done all the stuff.