If, having implemented all of our suggestions regarding sound quality improvement, you begin doubting the results and want to confirm them, start from the beginning, return your setup to its original state, and listen to the difference. Another approach is to make all improvements on the left channel only, and then compare it to the right channel.
The creator of Audio Tekne once performed an experiment: He invited several guests to an audition and discovered that, while approximately 90% of them stated that their sound had improved with Audio Tekne equipment, there were several people who thought the sound was unchanged or that it had even deteriorated. After careful investigation, it became clear that the cause of subpar results was the poor software, devices, parts and accessories used during the audition that had strong character. Sound had in fact improved, revealing all the flaws and shortcomings of poor quality equipment.
The human senses tend to acclimate to their environment. Take your time, and be sure not to jump to conclusions.
When you have a chance, go to an unamplified concert and listen.
If you decide to return your equipment to its original state for comparison, make sure you have first tried out the new setup for a few days. Once your ear has become accustomed to the improved sound, returning your setup to its original state will quickly reveal which sound is actually accurate.