Should I upgrade power cord for my preamp?

Power cord can make a difference with digital sources and pre-amp as well but for different reasons. Power amp is mostly about current delivery ability. Pre-amp is more about more control of noise. Results can be better clarity, resolution, detail, soundstage and imaging.

Audio Advisor is a nice resource. I have bought from them indirectly via Amazon for same cost plus I get points on my Amazon credit card when I do it that way, which adds some value.

I love their catalog. Reminds me of the old Lafayette or Radio Shack catalogs except targeting good sounding audio, and no low level parts, like resistors and capacitors, though I think you will find a fuse or two maybe. :-)

For pre-amp and source devices, especially digital,its all about noise control/reduction.

For power amps, its more about current delivery.

I use Pangea ac14se on both my ARC sp16 pre-amp and mhdt Constantine DAC at present. Each seemed to make things better, which I woudl attribute mainly to the shielded design of this model specifically for line level applications.