How important is EMI and RFI rejection?

1. Even decent equipment filters the AC line
2. Non-power line induced noise isn’t of a concern in the home environment (no large co-factors like multi-phase motors, baluns, etc).
3. I keep LV and HV cabling separated.
4. I run a fully balanced setup (outside of power at the wall)
5. All my equipment is chassis ground (as it should definitely be)

Simple steps using sound, best engineering, practices.

@jinjuku, I would beg to respectfully disagree with you on points 1 and 2.

Not sure how you would disagree with properly designed equipment, including in the umbrella of properly designed, not have needed filtration of AC mains: Transformer decoupled and Capacitor Filtered. 

Can we agree that EMI is going to show up as Voltage on the Outputs and it's going to have a FR characteristic (unless it's DC getting through which is a huge problem)?

On point #2: There just isn't EMI/RFI cofounder normally found in industrial environments. When we were wiring LAN and Serial for heavy stamping plants (think of presses the size of a small house and it was one of 12 in a large complex) along with CNC / 3 way milling machines. But up front in the conference room we installed Christie, JBL, Crown, Surge X and even though all in proximity no problems with the audio. 

Sorry but homes simply are not an issue. Even if we give credit to your 3D radiated emissions most homes are primarily stick and gypsum. HVAC being the biggest factor but it would only serve as an RF BLOCK.

You could put an HVAC duct 18" away from line level cabling and it's not going to affect anything. You could put a $400,000 scope on the output and you wouldn't be able to tell. 

If you don't have EMI/RFI then you have nothing to mitigate. And if you are worried? Get single ended IC's made out of RG59 that stuff is pretty much impervious. Or better yet balanced TRS or XLR. 

It's all about sound engineering and best practices using affordable, quality cabling and terminations. 

Then Goeff can get a measurement rig and show it. 

So EMI isn't measurable? The main source is AC mains noise and the harmonics. Using a frequency programmable power supply you can see this in action as you will see the fundamental change along with the spuria. 

Get an ADC and install ARTA will give you a host of spectrum analysis. Also there is the Dayton Omni Mic 2. 

Get a Schitt Modi 2 since it has basically no filtering on it's USB input and you can easily measure this.