When you try to listen to music in a quiet room with no external noise, I would suggest doing A/B comparison between your Alta and OPN to see how they compare, especially on the low ends where you perceive the muffling. Also it’d be interesting to pay attention to the bass performance between the left and right HA, just because your right hearing in the lows is much worse than your left, and I didn’t hear from you what size receivers you were fitted with the OPN. If it were the 85db receiver, it’d be under sized for your right hearing and for sure the 85db receiver won’t be able to give you enough bass amplification for your right ear.
The perception of the aid seems to be favoring some sounds above others maybe due to its constant scanning and rebalancing of sounds that it detects, depending the origin and distance of the sounds relative to where you are. It may also take a while for your brain hearing to adjust and get in sync with and get used to how the OPN does the rebalancing so that you can find it more and more natural over time.
With regards to your being strong and wearing it all day rather than giving up, I think you’re having the right attitude here and I think it’s critical to have the right attitude to get the most success out of the OPN. Some people may not like to have to deal with too many noise sources and come to dislike the fact that they have to hear everything and expect a premium HA to be able to snuff out the noises for them. These people won’t be successful with the OPN because that’s not how the OPN is designed with that kind of noise reduction in mind. Other folks embrace the ability to hear everything (including what they consider noise) and strive to learn to focus on what they want to hear and tune out what they don’t want to hear with their brain. On top of that, they also try to get as much opportunity to expose themselves to difficult listening environments as possible so their brain hearing will have more chances to learn and adjust. These folks will probably be more successful with the OPN and maybe will have a shorter period of adjustment as well.