I somehow deleted a long post. I'll try again but keep it short.
6 x OC 703 panels will help but not all that noticeable. Buy a bunch more as they will not go to waste.
For the biggest impact look at taming bass frequencies which creates acoustic havoc in any domestic room. Make 2 stacks of 3 panels placed on either side of your system. Set these up lying horizontally at 45 degrees straddling the floor/wall corner. If you get more panels do the same in other corners. The more you have the easier it will be to see the result on REW.
The best advice I can give you is to become comfortable with REW, especially regarding the CSD (waterfall) plots. Once you begin to absorb the lower frequencies which are, because of combining either constructively or destructively, creating peaks and nulls. It is difficult to appreciate the harm done by these peaks and nulls or partial nulls. Consider that a null has nothing to contribute to the sound, it's music that's missing. Gone.
Bass can be well smoothed by using a DBA but will still need cognisance taken of the decay time. Using acoustic smoothing in the modal region in addition to the multi-sub approach will optimise what can be done. This double attack on the bass gives stunning results.
I see @
tomic601
is the only one who wisely mentioned RT60. This mysterious quantity is simply the time it takes for the sound to decay by 60dB which for the average domestic room is about 400ms. The target then is to have the full spectrum decay within 0.4 secs. REW's CSD plots provide this info.
Expect a correct RT60 to provide bass info previously missing or partially missing depending on the depth of null and more control and bass detail.
It appears poor @
shalommorgan
did not go this route and required 5 iterations to get things sorted. Using REW or HolmImpulse (as used by Geddes), get the table off the net for RT60 for your size room and have fun.
The result of a correctly treated room is difficult to conceptualise but it is a bigger move to believable, rewarding and immersive sound than an expensive component upgrade. True story.