Modding NAD system: adding IEC & power cord ?

I would highly recommend you replace the stock power cord on your amp as well as your CDP. Hugh improvement. I just replaced the stock 18ga. cord on my Rotel dual-mono RB-960BX amp w/ a 14/3 Belden cord w/ a Marinco AC plug. I decided to not to put in an IEC chassis plug, but hard wired using wire nuts. Night and day difference. Used a "floating" ground wiring method on the AC plug end. Did the same w/my vintage Rotel CDP. Used the same Belden wire but I decided to use an IEC chassis plug. (Around $40 for a 6' PC w/Marinco IEC and AC plug.) Wonderful sonic improvement. Take Five Audio in Canada has all the supplies you would need. You'll be amazed at the improvement.

Suggest you replace the pre-out/amp in connectors on your amp with after market rca jumpers, if you have not already done so.
You could try a regular interconnect cable first, if you're skeptical about the benefits.
You will probably get a bigger benefit from this than trying to replace the power cord.

I made changes you refer to on an Onkyo DVD player, and it made a huge difference.

I agree w/Wainwright. It's highly doubtful that modding NAD's power cord is going to result in better sound. Just my opinion after having used NAD preamps for many years.

For a modest *bedroom* system? I think I'd be more inclined to invest in better quality source material and/or room treatment...

-RW-