Same here, I purchased a Ref 5, after much consideration never heard any major difference compared to the intergrated NFB 5.32 dac, so I sold it off.
I was offered a higher end USB cable when I got my NFB 5.32 way back at addicted to audio, and after a listen between the Generic and it, I couldn't hear anything personally. I have the T1's and even thought that the T1 was pretty impressively detailed on it and the treble was definitely brighter with that spike but never all that bad. Only prefer the Soloist all round for all my phones, T1 a little less bright to my ears (might be expectation bias). WA7 very nice due to tube's inherent distortion, even if not as clear as SS.
Maybe the old USB cable you have was a dud? Is that even possible?
Not a dud - I've tried with different generics too. Chord cable is consistently better.
According to a write-up in Hi-Fi News UK, there are many USB cables that don't necessarily perform significantly better than the generics or that alter the sound too obviously and cause imbalances such as too much bass, too much treble, etc. I found the Chord to be really good.