Help in designing a control room

Hello friends I would like to help me with the acoustic design of my control room, well, is a room of my house that modify off the edges to avoid room modes etc, this I did it with drywall panels, we locate absorbent panels rock wool 5 x 61 x 122 cm as shown in the photo, on the corner right behind me I made a serious trap which occupies the entire top of the room (2.40 m) with a 30 cm produndidad to the side I have planned to build two broadcasters diaphragmatic 20 cm x 50 cm high lake and a QRD diffusers, but it is there where I have the restlessness "since I often minimal QRD diffusers? I had thought of them from 650-2600 Hz, then, so they are not very deep so the little space I have, "I would need more coverage? , Okay that range according to the size of the room? .. Thank you very much in advance for your help

Is that closet movable? If yes, move it to where the monitors are and flip the entire layout of the studio to start with. So monitors etc. before the wall on the bottom.