One of the first mods I did in my system some many years ago was to change the typical Japanese Mylar caps that Onkyo used across the diodes in the bridge rectifier.
I changed them to Wima MKC10s Polycarbonates (from memory) as I had them, they fitted the PCB space and were the right Voltage. It made a very noticalble improvement in the high end and I think the image was improved.
I think the original Mylars (sometimes called Green caps, in Australia at least) were of a fairly inductive type as compared to the stacked foil Wimas so that may have been a factor?
Eventually I improved that Amplifier to death
I'd try the Cetramics as long as they are good multilayer types.