Is it all in my head??

Far more likely that you are hearing a difference than it all being a figment of your imagination. 

waltertexas

If you like the Kimber cable sound and improvement then 
maybe you should stay with using Kimber cables and move up to a higher grade that they make .
Synergy can be an elusive find , so changing cable manufactures could prove positive or negative sonic effects .

nonoise makes a good point , you've started now go from there .

@nonoise,

Maybe I didn't see that you were addressing the OP and not the thread??

It's partially my bad. 🤔
The thread started with power cords and kind of went off on ICs and SCs and I just ran with the last few posts concentrating on speaker cables. 

Some of what I listed can still apply with PCs since not all power supplies are made the same and not all power sources are either when it comes to noise, wiring, substations, geography (as was pointed out on another thread where in the North East, the power somehow corrodes outlets at a level not experienced elsewhere-I'm sure weather has some factor in it as well).

Where I live the power is really quite good and regular, not varying +/-2V all day long and yet every PC I have sounds different. The three best I have are the TWL American Digital, with the Cullen Red Copper and Zu Mission coming in second, with little difference between the two. 

They're all made well with quality parts yet they're all made differently, and they all sound different. I can't explain it.

All the best,
Nonoise

Roger on all that. Thanks.