Clean AC power

You will need an oscilloscope to see the sinusoidal waveform of your AC coming into your home. If you're dead keen on seeing it, that's what you want to use.

What you use in your house / stereo system will introduce noise into the supply, especially localised noise.

What I liked that sold me on the idea of the Puritan PSM 156 power conditioner is the no nonsense approach. Twin transformers to allow for good current flow with no bottleneck, DC (direct current) removal (also can been seen using an oscilloscope) and each receptacle is isolated from each other by using a high pass shunt of electrical energy to ground, from both neutral and active, individually. It also has circuit protection.

And it's one of the least expensive, with the most features.
I'll admit it, I am a performance buyer, with limited budget - so it had better perform!

@jea4 - yeah when I'm opening a panel with 3 phase VAC I step to the side and have had some pretty interesting looks when I've told people to step aside and move way back, and I'll absolutely wait for them to comply.

The PPE I have worn when training for 480 three phase, gave me some idea of how dangerous even that is (high joule rating). ISOLATION. Lock out, tag out.
Anyone doing electrical work on their own home, I would highly recommend purchasing an AC detector pen.
https://www.walmart.com/ip/Klein-Tools-NCVT-5A-Non-Contact-Voltage-Tester-w-Laser/996218143
I often use it to quickly troubleshoot motor controls, easily finds faults on three phase monitors, motor starters etc. (and then I break out the Fluke). And if it's right there I'll wave it over the conductors just to be super sure, I've absolutely isolated the correct circuit.

Almost every test in my instrumentation course I did, covered how many milliamps it took to stop a heart. 

Electricity in an electrical panel is

nothing to treat in a casual manner.

.On that I can 100% agree.