Power Conditioner vs A/C cables

I decided I need power conditioner with filtering and strong overvoltage protection anyway.  I bought Furman Elite 20PFi and placed it on the shelf below DAC and amp.  I concluded, that if power cables have effect on sound, it will be proportional to the length of the cable.  I built very short (1.5ft) shielded cables using Belden 83803 and Wattgate connectors.  

I believe that good power filters are very useful. Both to filter your AC, and to block digital noise from the digital/switching power supply components (computers, TVs, other). This means a mains filter AND a 2nd one, can be fairly simple, just for the digial /switching stuff.
Power cords i have tested many times and fail to find an value, unless you are replacing something deficient- which is not all that uncommon, but easily avoidable for $20

A power condition that generates its own pure sine wave output is worthwhile to completely remove line noise.

Shielded power cables stop Electromagnetic Interference emanating from the cables. Certainly EMI is present in the environment, but it is still important not to add more in close proximity of equipment.

If you are really serious, both are crucial!

Power ‘filters’ are terrible, they normally take more away than help the sq. You want a power regenerator or use balanced power to get the best out of your system.
How much to spend or how much improvement you are going to hear all depends on the quality of your system and your hearing. To actually state the a $20 cable is all you need is foolish for example, even a pioneer system would probably see an improvement with a $20 cable. A dealer friend did a demo for me on a system that cost around $20k. He made 1 change that I couldn’t see what he did and it made a huge difference in sq. All he did was to replace the stock power cord on the Mcintosh amp to an entry level red dawn nordost power cable. This was almost 20 years ago and ever since, I have always used the better power cords on all my components, which have been much more expensive than the red dawn

Ralph, at Atma-Sphere has one of the best Power conditioners you can obtain at the moment. Elgar Units that were made many years back still are much better than anything made today. It a proper Labtory Power condition using the fastest response time.