Accuphase E-5000 factory power cord good enough?

+1 @jl35.  I use after market cabling as well. However,this is really only a decision you, and your ears can make. 

Power cords, and all cabling, a hotly debated question here, hundreds of threads...easy answer is purchase a few that offer full return...I use aftermarket cords but many won’t/don’t...though if it sounds great, clearly your cord is good enough...if good enough is good enough !!!!  With an amp as good as yours I would certainly want to try out some cords to see for myself in my system...