Room treatment

The best thing you could do is to create a virtual system and post photos of your system and space. Without understanding your system and environment it will be very difficult to help, They need not be glamor photos. Just grab you phone.

have you done any analysis in REW with data to determine that the room is truly overdamped. What speakers do you have? You failed to mention that. Cos what you described isn't an overdamped room to me.

A room that sounds overdamped in our part of the audio space must have an ET30 of less than 100ms

I doubt your room has that @jrdavisphd unless you provide a concise data set from REW

+1 @kofibaffour get a mic and use REW to analyze the room.  You can send the result files to somewhere like GIK and they will make recommendations.

You could also try toe-in the speakers pointed directly at your ears and near field listening. You'll hear more speaker and less room.

Not knowing Speakers Models used,  does not assist with attempting to understand their compatibility when used in a particular volume of Listening Space.

Without making an outlay of any substantial monies apart from maybe purchasing a Speaker Cable with an extended length? Along with a 3" Decorators Cream Coloured Masking Tape and a couple of Low Profile Skid Trolley's to make moving Heavy Speakers much less of a chore.

There are investigations that only require an Open Mind and Time, ( Time being the most important as some configurations produced are best lived with for a while to fully relate to what has been produced with an End Sound).

Symmetry is ones friend when it comes to Stereo Set Up for a Speaker.

The Masking Tape will be used to demarcate different positions on the Floor to place and Orientate the Speaker, the 3" Thick Tape, allows for additional demarcation to be put on the Tape in 1/2" increments, ( When finely tuning a Speakers impact on how the ear is to receive and perceive an End Sound.

The 1/2" incremental changes to a Toe In can be the cherry on the cake in audio, where speaker set up is the concern.

The same demarcation can be done for Listening Chair if a single chair is used in the Sweet Spot. If the Chair is usually against a wall, make the first position 5ft -1500mm set off the rear of the chair from the wall, and then use 1ft - 300mm demarcations back to the wall.

The Speakers rear face can be off set from their behind Wall up to 4ft - 1200mm and then returned towards the behind wall, as close as can be attained in 300mm increments, making sure equidistant dimensions are used for each speaker. 

Start with Speakers at 4ft into the room and with the Speakers Inner Sides @ approx' 8ft - 2400mm apart.

The Front Baffle set at 180 degrees to the behind wall.

The Speaker Side Wall being an equidistant dimension to the rooms side walls.

The 'Toe In' that can be tried out, can be done in 1/2" - 12mm increments up to 3" - 75mm.

The distance between Speakers can increase by 18" - 450mm, to increase the spacing to the point that they can be as close to the side walls as possible but remaining to be an equidistant dimension. 

If the Speakers are set up with the 4000mm dimension as the behind wall. I would assume there are close to 24 Positions to be used to set the Speakers up in, with 5 x 'Toe In' positions for each Position selected, Hence the skid trolley's suggested.

A Spirit Level is needed to make sure the Speaker side wall is plumb.

The Font Baffle can have a Lean towards or away from the listener, ( a little further experimentation for the Speaker Owner)

An ideal Speaker Placement will be discovered for very little monies if this method is undertaken.

Methods for Mounting the Speaker are another investigation worth considering once Speaker placement in a particular space has been resolved.

For quite a large number of speaker users, a rethink on mounting the Speaker has produced results that have been reported on for being discernible as a betterment.

Coupling a Speaker to a Room using Toom Acoustic Treatments to manage energies produced in the Listening Space is not needed to be the first port of call.  Such designs for a structure to create an improved interface for produced sound does not need to be costly,(mainly Absorption or Diffusion are the fundamental purpose of structures selected to be placed in a Listening Space).

Gdaddy+1

Try opening the curtains.  Not ideal as on one side but glass is lively (usually bright) vs curtains are damping.