please do not be duped into chasing power cords and other electrical devices to tune your system. I have yet to see any true evidence that such things matter to anybody that doesn't have money to waste. Most reviews for such items show at best no degradation of signal compared to the stock item. Other gear can actually introduce signal limitation or in the case of some "power conditioners" actually restrict the electricity flowing through them to whatever is plugged into them.
I will not endeavor to tell you what you should do, but please know that I am on a Marantz 6012 and while it may not be earth shattering, it works quite well, and was a significant upgrade from what was a 10 year old Onkyo. The Marantz in 2.1 or 7.1 delivers my fair share of goosebumps and HT splendor.
Most of the time, here, we spend energy helping people understand that upgrading processors is not a guarantee of improved SQ. It seems you went from a good processor to two years newer and a step up the ladder. It may seem like there should be a "veil lifted," but many will say this is not the case. Please do not be discouraged. Your AVR should at least sound as good as the previous.
I hope you will stay patient with your process and keep working to make certain you are set up properly!