How to replace hardwired stock power cord ?

Unfortunately, there’s no, "standard" size for IEC connectors, so no one makes knockout punches, for those animals(to my knowledge, at least). Some rectangular punches are available, but- the prices typically aren’t realistic for limited usage(ie: https://www.amazon.com/Greenlee-60031-Rectangle-0-750-Inch-1-140-Inch/dp/B00204DWQI ). I’ve modded a few ARC preamps, which had aluminum chassis(easy to drill/nibble/file to shape/size, without a lot of metal flying around). No familiarity here, with Nak’s later(digital era) chassis materials(was steel, way back when). With a, "captive" cord in steel: I’ve found it easier to install upgraded cords like the following Zu examples(round/small diameter), can be installed through a rubber grommet, without any chassis alteration and soldered, internally. Of course, if you wanted a larger cord and don’t care about modifying the chassis: enlarging the original hole with a drill or knockout and using a bigger grommet’s an option. https://www.zuaudio.com/cable/mission-power-ii If you can find one of these, you’d be hard-pressed to improve on it’s performance (with a CD changer/DAC), at a reasonable price point: https://www.zuaudio.com/classic-cables/mother-power-cable

As far as your unit’s capacitors: if it were me, any electrolytics would be replaced with the exact same values, in either Elna Silmic II’s, their Cerafines or Sanyo OS-CONs. Most DACs have regulators that can be upgraded, as well, to great effect. (https://www.partsconnexion.com/capacitors-ele-elna-rfs-silmic-ii-series.html ) (https://www.partsconnexion.com/capacitors-ele-elna-roa-cerafine-series.html) (https://www.partsconnexion.com/sanyo-os-con-electrolytic-capacitors.html) (carefully observe polarity, when replacing electrolytics) (https://www.partsconnexion.com/belleson-SPX78-regulators.html

Thanks rodman99999........well I had hoped to replace it with Furutech    https://www.futureshop.co.uk/accessories/connectors/iec-power#page=1

I don't mind cutting out the rear side of the case to accommodate this - but then - is soldering just straight forward ? 

I have no experience in changing the capacitors ....wish I could. However thanks for the info....much appreciated.

Soldering: Yes. Just follow the existing cord, to it’s connection points. If there’s a star ground, the new cord’s ground conductor to that(perhaps you’ll need an eyelet/ring terminal). If not, try a point on the chassis. If that creates a ground loop, just forget about(cut off) the cord’s ground conductor(you didn’t have one prior, anyway). Same ground rules apply, for an IEC connector, if you choose to pursue that course(per Erik's recommendation). If you can solder/desolder competently at all; capacitors shouldn’t be a problem, providing access to your PC board bottoms is possible/easy. Be adventurous, but- practice first! Tiny alligator clips make great heatsinks and eutectic alloy solders are pleasure/easy to use, if you decide to go there. btw: Elnas for signal path / OS-CONs for power supply