That is too what i observe in general.
A while ago, i had the Phis and a friend too, and we decided to organize some tests using a very powerfull Moon amp, to see if the superconductor performed better in A/B blind tests and also comparing the sp1000+amp and the Moon amp.
Here’s a few pics, we were 3 testing them.
The results were interesting. Here’s the link to our french forum if you have the courage to translate
But basically, the diana Phi for me did scale up significantly using the Moon or at the time i had an Auris Ha2. But the A&K dap was very good too.
And for the cable, the superconductor was more opened, had more energy, and more controlled bass and body. However the stock cable had more clarity.
So conclusion was it was not a must but just different sound proposal...
For instance, we were 2 prefering the stock cable.
http://www.tellementnomade.org/forum/viewtopic.php?f=309&t=24039&start=285
I will be able to tell you soon. I also did the same and bought the he adapter to connect my speakers (also harbeth p3esr) amp, a lector audio zxt-70, it’s a hybrid tubes/MosFet amp delivering 2*70w in 8 ohms in pure class A. Was planning to try this week end. Will post here my feedback