I cannot speak to your particular kit but I can offer a parallel hands-on story.
I had a NAD C370 integrated amp in a prior "B" system. It came with a stock hardwired power cord that paled in comparison to a quality build external one vis-a-vis actual cable quality and gauge, the cable design, the cable sheathing, and the crummy quality of the male plug.
I had the amp professionally modded wherein the stock cord was scrapped and replaced as follows:
- Back panel dremmeled out to accept a quality build female IEC receptacle
- Inserted a comparatively very modestly price $125 quality external power cord (a much thicker and better gauge wire also terminated with quality Wattgates ) now plugged into hospital grade wall receptacles. The comparatively modest price strata of the NAD integrated amp itself and resulting performance capabilities of the kit itself at that price stars was a guideline as to how much my power cord outlay was going to be
The improvement was immediate and it was not subtle: more slam and attack and overall improvement in body that was previously missing .... Well worth the added investment in my case. I experimented later with much better cords (and muchos ka-Ching!) swapped in from my "A" system without any further measurable improvement in the NAD's perfirmance ... There is a threshold after which it made no sense to go hog wild.
It also actually facilitated the amp's eventual sale as a preferred added feature to the buyer, and I also recouped a good part of the added outlay.
Most gear is built to a cheapest-U-Can-go price point, and "stock" hardwiring is a very common occurrence .
I agree with the prior post that an assessment of cost versus added benefit need to be revisited FIRST with YOUR system.... One-size does not fit all.
The only hardwired "stock" power cord I have is in my HT Vandersteen subwoofer, but it is a clone of an external quality cord anyway and expressly matched to the internal amp by the mfg.