Re the Isotek. Have you tried now taking it out the system. I auditioned Isotek a while back and found it choked the sound I do agree a filter is necessary though, just not that one.Save yourself a fortune: do not upgrade until you got your foundation right! See my post in the Tweaks forum.
I have a similar set-up. The problem is (i) internal resonance/ vibration of the equipment itself (ii) unclean power.
Solve (i) with proper bases/ pucks and (ii) with a power regenerator (I use Isotek Mosaic) and the best power cords money can buy (buy 2nd hand!). But (i) remains paramount. Your system WILL sing!