2 prong power cable

Are the two prongs on the original cord identical in size? If so the first thing I would try is reversing which prong is inserted into which slot in the outlet.

Any recommendations for PCs that help with imaging and maybe deepen the soundstage?

From a technical standpoint I doubt that can be predicted with much if any confidence. I would expect the sonic effects that may result from upgrading the cord to depend as much or more on the specific design of the Marantz unit, and on the voltage and noise characteristics of the AC at your particular location, and on the technical characteristics of electrical noise that may be coupled into the Marantz from other components in the system, than on whatever intrinsic sonic characteristics the cord itself may possess, if any.

Good luck. Regards,
-- Al

Jea48 8-5-2016 10:41pm edt

The 2 blade male plug is polarized.

Assuming the OP lives in the US or Canada. His profile Country is n/a.

Thanks Jim. Prior to submitting my earlier post I had found this photo of what is apparently the power cord on the OP's Marantz integrated amp. It’s hard to tell for sure from the photo, but it looked to me as if it is likely to be non-polarized.

Under current USA regulations is polarization a requirement for some or all consumer electronics having two-prong power plugs? And if the answer is "some," do you happen to know what factors determine whether it is or is not required in a particular case?

Best regards,
-- Al

Thanks Jim. Note 9 seems pretty generic, so I wouldn't consider it to be definitive (as I'm sure you wouldn't either).  The OP seems to post here fairly regularly of late, so I’m sure she’ll let us know.

Best regards,
-- Al

As is usually the case I agree with all of Jim's (Jea48's) comments.

What does a shielded PC do that wouldn't be good for the amp?

It won't do anything bad for the amp, but I believe Jim was just saying that he suspects an unshielded cord stands a greater chance of changing the sonic character of your system in the direction you prefer than a shielded cord.  I agree.

When you say "install a 20 amp dedicated branch circuit" do you mean on the circuit breaker panel in the basement and how will that change the sound?

This refers to having a breaker in the panel and wiring from the breaker to the outlet that powers the system that is dedicated to the system, and powers nothing else.  It is considered to be good practice from a sonic standpoint, and often seems to be sonically beneficial, but how it will change the sound in any particular case can't be predicted with any certainty.

Presently the amp is just plugged into a surge protector extension cord along with 6 other things. Is that bad?

If it's an inexpensive surge protector that is intended for general purpose use, it could very well be having adverse effects on the sound, to some degree.  If that is what you are using, at some point you may want to research past threads here about surge protectors and power conditioners.  As an experiment, it may also be worthwhile to see how the system sounds with the integrated amp plugged directly into the wall outlet, while the rest of the system is plugged into the surge protector.

FWIW, I've had good results with this BrickWall surge protector I used to use, and the Audience aR2p surge protector/power conditioner I presently use.  (The latter used in combination with a Wiremold UL210BC power strip to expand the number of outlets).  There are many other choices that would be as good or better, of course.

Good luck.  Regards,

--Al