Anyone had the equipment customized ?

The problem with some "modifiers" is that they simply "upgrade" parts by substituting more expensive and currently trendy parts without considering the impact on sound.  Some parts choices, particularly with higher end gear, is determined by voicing the component, not just by picking the cheapest thing that will work.  It is not automatically the case that a more expensive part will sound better.  For example, I spoke with a builder who said that in his designs, the expensive, super tight tolerance Vishay resistors sound terrible, and I know a couple of builders who also prefer "cheap" carbon composition resistors.  Same goes with caps.

A local dealer who employed a builder to make his own house brand of tube electronics once asked me to listen to one of his amps.  To me, it sounded bad compared to other amps he had built for him and I got up the courage to tell him that his amp sucked.  He was actually happy because what he did not tell me ahead of time is that this amp had been sent to a modifier by a customer who did not like the result and wanted it fixed.  The modification involved Blackgate capacitors and teflon caps, etc.--all the latest rage.  

That does make a lot of sense.  Rail to ground decoupling caps work much better at killing noise when they have a moderate amount of ESR in them while DC Blocking caps passing a signal work best when ESR is held to a minimum.  

I’ve upgraded my phono stage with a Burson SV6 Classic and regulated power supply. Soon to modify my integrated amps to bypass the integrated phono stages. 

@spatialking said:

Rail to ground decoupling caps work much better at killing noise when they have a moderate amount of ESR in them while DC Blocking caps passing a signal work best when ESR is held to a minimum.  

That is incorrect. ESR in bypass capacitors reduces their effectiveness. The goal of bypass capacitors is to stabilize Vcc and displace noise to a part of the power bus that has higher impedance than at the point of consumption. It is  the lower impedance in a voltage divider. The lower that impedance is with respect to the upstream part of the supply rail, the more noise is displaced there. 

That is the often thought philosophy.   It is a small amount of ESR, which dissipates the noise energy as heat, rather than dumping onto the ground plane and causing ground bounce.   Sure, a cap with large ESR can cause a spike on the chips power pins, what is needed is a small amount of ESR in a bypass cap to dissipate that spike as heat.     

Some large computer back planes have shunt VHF caps in series with a 1 to 10 Ohm resistor to ground just to keep the power plane resistive and lossy at higher the frequencies where typical bypass caps have gone through their internal self resonance.  

For series DC blocking caps, then, yes I totally agree, the lowest ESR cap is best.