Norm, Here's the thing: The lamp cord, as I recall, is/was hard soldered to the PS. Then when you ditched that you or someone else installed an IEC connector, to which you plugged in the Nordost PC. In all my audio experience, NO connector has always sounded better than ANY connector, no matter how wonderful and Furutechian it may be. Thus, if one were to posit that the PC makes a difference, the IEC connector might swamp out any such difference. Here's where I admit that I hard-wired a length of XLO power cord (which happens to be my favorite) directly into the PS of my SP10 Mk3 and hear...... no difference. But I felt oh so much better.
However, to my surprise, PCs to power the bias supply did make a difference to the sound of my Sound Lab ESLs. Go figure. In that capacity, current carrying capacity of the PC is moot; the bias supply requires very little current. I generally think that sonic differences among PCs are 90% due to current carrying capacity, thicker is better. But there are obviously other factors.