Most overlooked part of your system?

There is really no easy answer here. You can go in so many different directions. However, with some careful selections you can accomplish a lot with little investment. Dedicated lines are a good start. Go 20 amp on the dedicated line if you can. Choose good quality outlets. You don't have to spend a lot here. Porter Ports sold by Albert Porter here on Audiogon are very good, as are Pass & Seymour. If you want to spend more then I suggest Oyaide.

Cabling does make a difference but as Tholt mentioned you will get more bang for the buck spending the extra dollars on better equipment. It's a lesson I learned. I've downgraded my cabling and upgraded my equipment and the sound is for the better. You can get some very good cables like Oyaide and Grover Huffman that won't break the bank and perform quite well. I'd budget more for power cords and recommend something like the Oyaide Tunami, Tel Wire, or entry level Fusion.

Isolation is also something you can go over board with. Since you only have the two components I'd recommend looking at the Timbernation stands that are made of solid wood. Then you might consider some of the Heribies footers to use between the component and platform.

Mattcone

Definitely, go with 20A.

While that's going on add in a good outlet... or two, making for a four gang power portal. Hospital grade or up.... Porter, Oeida, etc.

One never knows.

Wires do make a diff. How much depends on you, your gear, and how much you wish to invest there.

Get a good to as good as you can justify, speaker cable. Then address the power cables... lastly, do the interconnects.

Lots of info here on isolation and it's various applications & philosophys. Resonance, physical, and electrical.

I've determined no actual ratio for cable costs vs. component costs. More importantly I address each component individually in that regard.

There's about 81.705 gigazillion cables available. ya can't try em all so get in where ya fit in there as well as you can justify it.

Such a tidy system as yours shouldn't pose too many problems with wires.

Good luck.

I was intrigued by the title of the post, but disappointed to read that it was about cabling. I believe cabling can make a difference, but as has been said already, not as much as the components themselves. If the title were posed as a question I would have definitely said the room. That also can make a HUGE difference, and I'd look to investing time, effort and $ there before exotic cables. The potential for the room impact is far greater than cables IMO and in my experience. As far as the cables themselves, IC's before PC's. Source (to pre) first. That'd be my approach anyway. Clean, isolated power will have more bang for buck than just sticking in an exotic PC. If you pay an electrician to run a couple of isolated lines for your system, depending on your house, it may run you less than many fancy PC's, and, again, bigger bang-4-$.

A moderate investment in scotch, bourbon, tequila, wine or herb will reap
benefits well beyond the same dollars spent on wire, isolation or other
audiophile tweaks.

I doubt pouring any of the aforementioned on your stereo will make it sound better, but its worth a try.