Your system is very well matched/balanced as it is. I was just commenting that the speakers are not the limiting factor here. Your cable upgrades suggestions are also a good match for that level of equipment, so maybe you should start there. It you can borrow, try a few brands of interconnects. CD player performance tends to vary more than other components with different cables.
If you don't have one; then something like a Audio Power Pack II power conditioner will quiet the background some. Whatever power center you choose; get one that filters the digital separately from the other components.