i hate to say that cables make a difference in audio. but i've to admit they do. my system is mcintosh MCD500, preamp C48, amp MC302 and cremona auditor M.
before my use of nordost heimdall 2 power cords to preamp and amp, i use REL 328 sub to complement (for lack of better words) if i feel the need for some additional bass.
the c48 has an equalizer (hopefully the purists dont curse by me saying this); before the heimdalls, i often tweaked it to be with more treble as well.
once the heimdalls are in, i rarely use the sub! the bass and treble feel just right. my listening room is 4m x 4m. and the highs seem to be extended, more detail and even non-audiophile redbook CDs sound great (taylor swift, radiohead, and many others). so i agree that nordost's higher priced cables to be more revealing but "unforgiving" is not a term i would use.
i paid US$ 2,000 for both PCs but am not regretting it.
i am very sure others' experience will differ, but am a happy owner.
i was told that heimdall 2 has 90% of valhalla's performance (whatever that means) but for now i can only afford the former.
let's enjoy the music!