Will line conditioner do anything for the other receptacle in a duplex?

I'm going to recommend what I just bought: Dave Elledge's P.I. Audio UberBuss.

Best conditioner around. And fair price as well.

Clearly I really need to stack my Bright Star Little Rock on top of my Puritan PSM 156.

Hello,
The Puritan PSM156 or PSM136 will do this. It filters out over the air signals like WiFi, cellular, and Bluetooth. It also filters out noises from DC, compressors, and switch mode power supplies. It is incredible. If you are in the Chicagoland area this store lets you try before you buy. https://holmaudio.com/
They also have the Guardian power plug filter. 

My understanding is that the EP -2050 (https://store.acousticfrontiers.com/products/environmental-potentials-ep-2050) and perhaps the modular devices operate by serving as the preferred conduit for the noise in the signal. The EP-2050 functions in a similar way for surge protection. Any backwash, RFI, etc. that makes it to the distribution point (panel/outlet) Is essentially siphoned off preferentially, making it unavailable to other lines on the same circuit. This would be all circuits on the main panel for the EP2050 and the other outlet in the duplex for the modular device.  

I would think the line conditioner would serve as the preferred conduit in my case, leaving a cleaner signal to the other outlet. 

Theoretically correct?

The EP-250 looks like a good device, although I have no knowledge of its performance.

I’m not sure you fully understand the benefit of this device. There is no preferred conduit, this power conditioner/surge protector "cleans" the noise in all the circuits at the panel. This includes dirty power from outside and noise which has been generated within the house (appliances, furnace). So, noise in all lines is reduced, possibly a modular conditioner is not needed.

The line conditioner plugs into a receptacle and starts its "cleaning" at this point. All components will have less noise and SQ should be improved.

The other receptacle in the duplex is being cleaned by the EP-250 conditioner. The line conditioner serves only the one receptacle, and it is only cleaning the components plugged into it.