I also have been doing battle with a bad sounding 10'x10' bedroom studio in my house for years. I have spent countless $1000's of dollars trying differnt methods of getting things to sound right. One thing that helped is going from larger studio monitors down to Yamaha HS-5's.
Then I remembered one of my former guitar students has been the house engineer at Tommy Lee's studio for years. He has worked with Motley and Mick Mars tone and also Phil X and John 5 and grew up on the same old school sounds I like.
To avoid confusion, the following picture is not of my home studio, but Tommy's studio
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So I contacted him and found out that he has his own bedroom at Tommy's house, but also lives just 15 minutes away from me part time also. I explained my situation and asked if I could hire him to come slum it in my home studio for the day and help me capture my guitar sounds. He was willing and about 2 weeks ago he came over.
Biggest takeaways, he uses the exact same Audio Technica ATH-50X headphones the original poster mentioned he already had. He prefers those $150 headphones because his mixes on them translate very well to listening on most other systems. He also said I listen to my monitors way too loud. Now I am trying to get used to listening at the level he kept them at. As also suggested earlier in this thread, he very much likes the Waves CLA NX for mixing in those headphones. He said that he has mixed many professional albums at home in his own condo with headphones and very moderate volume on his monitors and never had the neighbors complain.
He said I will never like the way my room sounds. That all the treatment in the world won't make it a good sounding room just will make it less and less horrible sounding. That headphones and my studio monitors at a much lower volume are the cures and learning my room and how mixes in those headphones using the Waves CLA NX and learning how they translate to other systems and compensating will have me happy with what I am doing much more than trying to treat a room that won't sound good regardless.
It was a full day of so much information and never hearing my recorded guitars sound better that is was almost too much to take in but this my best memories of what I got out of it.
And regarding "carpet", a 7' x 9' area rug in my 10' x 10' room certainly helped with the reflections.