Honestly don't think it matters which one, if it is a good power cord it will make the same improvement whether on a DAC, pre-amp, amp, etc. Don't take my word for it, move them around, see what I mean. What does make a difference is if you upgrade your worst PC vs your best. Obviously if you have one that isn't very good it will be a lot easier (cheaper) to hear a big improvement than if you try and improve your best. This will be true regardless of what component it's being used with.
Put that pre-amp on some Townshend Pods, you will be surprised!
Put that pre-amp on some Townshend Pods, you will be surprised!