Parasound P/LD-2000 preamp mods?

The P/LD-2000 does have some impressive circuit design such as dual mono topology, pure class A discrete circuitry, direct coupling, 92,000 uF of capacitance,etc., and pretty high quality parts such as lots of Black Gate capacitors, Nichicon Great Supply capacitors, Vishay resistors, etc., but, I do have to wonder about the silver-plated internal wiring, and the quality of some of the feed-back resistors, diodes, power transformer, bypass caps, etc.
I just wonder where the biggest weaknesses are, and which parts would bring the biggest improvements?

Thanks for your very detailed reply, John!
Lots of useful information in your post.