jylee, consider yourself lucky that you do not have to spend money on power cords!!!! Thats what makes this hobby so fun/frustrating. There is no formula or right or wrong. For me, I was not a power cord believer until recently. From my experiences, power cords make the biggest difference on the source, but I think this is dependent on the source. In my system, power cords made a big difference on my Esoteric cdp. I have found power cords to make less of am impact on my Pass amps. I will audition the SR Precision Ref and Hologram A on my amps though just to verify that I do not hear much if any difference. The same with my previous preamp, Audio Research Ref 3. The stock cords sounded best.
But as mootsdude pointed all, power cords (and everything in this hobby) is dependent on synergy as well as a myriad of other factors and variables. If the right mix of variables allows power cords to make a positive difference great. If not, consider yourself lucky!