While both can make a difference, I think for this particular component you will get far more impact per dollar with tube changes. After a tube change, try upgrading the stock cord with an inexpensive 14/3 generic IEC. If that helps, then down the line you may want to play the PC game more directly. Also, unless you're going with top shelf high current power conditioning, you may wish to plug this amp straight into the wall. Lastly, before spending several hundred (or thousand) dollars on power cords, first spend less than that on getting a dedicated circuit installed. You'll be glad you did.
