Does preamp w/Power Supply need a good Power Cord?

Yes, it will make a difference. You can get an Oyaide cord for 2-3 hundred, I use them. Also use Siltech, Spirit Sound has some demos beginning at $60 for 1M. I didn't use them for years myself, but it can make a big difference.

I good company to deal with is VH Audio..You can prety much have them built any flavor you want and at a reasonable price..Also easy to deal with..

Not knowing you situation, system, or gear being used... there are a few Tg Audio HSR-i gen2 cords on Agon now, that for the $$ can't be touched. Esp with Solid State gear... They will greatly improve your soundstage (focus, layering...) and PRaT. A good barometer from which to base improvement on if you move up the ladder to more expensive cords. Not afiliated in anyway with the seller - just a Tg Audio fan myself...

I have had a number of preamps with separate power supplies (Audible Illusions, Blue Circle, Joule Electra, Pass Labs) all have benifited from the Ac cable upgrades!

Obviously after spending a kilobuck you'd better hear some differences and besides, good contribution to help out with today's crisis situation as well.

Thanks for the response. Got an Oyaide, wow! Sounds great across the spectrum: big upgrade in soundstaging, bass, and detail. Heading over to Tokyo in a couple of months, will probably bring back some goodies! They can be a had a bit cheaper over there, according to their Japanese web site. Thanks for the tips!