Although you posted this post a long time ago i don't think that the answers that have been given here really helped you and besides, allow me to use your problem and answer for those who has similar problem....
Well first of all, about the furniture of your room, in an ideal room you would have got rid of them and replaced them with lots of outboard, acoustic treatment and probably a sofa for your friends/clients right? but this is,of course, not an option so forget about that and try to focus on what you CAN do, leave the furniture as it is.......Having said that, the furniture in your room DOES take a very important role in the overall acoustic treatment...(after all, the bed, table and closet help with absorbing mid- and high frequencies in a sufficient way)
Moreover, moving the Monitors away from the wall would be the first goal......in other words, try to move the table towards the center of the room, making a 1 meter gap b/w the rear of the Monitors and the wall.
The table would be positioned in an odd way (not flat against the wall) but it is vital for the low frequencies.
If you really cannot achieve it and there is no way for you to move the table further more towards the center of the room, try to use the Low-cut filter of your Monitors(......if there is one.....) to cut everything below 80 Hz in -3 dB.
That should tame the 'Build-up' of the low-frequencies due to the proximity of the monitors to the wall......
You need to bare in mind that keeping the monitors away from walls is a fundamental basic and i would recommend keeping them at least 1 meter away from walls.
Anyway, that''s not sufficient though, and you will have to locate Bass Traps in all 4 corners(ideally) and you might need to use some more in a wall-ceiling feshion....it all depends on the size of your room and how it behaves below 250-300Hz, but a good start would be 4 Corner Bass Traps, located in each corner of the room. It can be installed very simply,does not take so mush space and requires only 4 drills for each Bass Trap and yes, it can be removed and reinstalled easily.
You won't have to worry so much about the mid and the high frequencies as mentioned before, the furniture in your room does a good job and besides, Bass Traps absorb mid&high frequencies very good (0.8,1,1.4!!) so if i were you, i wouldn't pay so much attention to frequencies higher than 300Hz. It might sound radical yeh? people use to work with materials like 'Sonex' or other overpriced materials but they forget (or don't know...) that the real issue is the low-frequencies(you said it yourself didn't you?)
and like i said before,Bass Traps DO great job with most of the frequency range (up to 5KHz....) and porous materials like 'Sonex' does NOTHING to anything below 150Hz.......so think twice.......
What you SHOULD DO with 'Sonex' sheets is locating them on walls and ceiling( yes,ceiling!!)in order to absorb and thus, eliminate the Very-Early Reflections. The reason for doing so is to increase the clearity of the original sound and improving the stereo image. There are more reasons for doing so but anyway you look at that, it is important as locating Bass Traps and than again, it is easy and simple and does not necessarly requires a lot of 'Sonex'......just a few of them located in a very specific place on the wall and ceiling.
Last tip for you is to put a heavy carpet on the floor (you know, those old ones that safta has) and also a drape for the window. it would help tremendously........
Bass Traps are easy to build and you can find lots of information on the web
This is a brief summery of what can be done.....but of course,a lot more can be done and didn't mentioned everything,hoping that someone else could add from his knowledge.
i hope i helped you or others....