Paul has commented that Marantz has a "house" sound that manifests itself due to some similar design principles that are used across many of their players. His mods revise what he feels are the errors they have made.
I am in the process of burning in a Marantz 9500. It has the latest Crystal dacs, an updated HDAM output stage, etc. etc. but I am hearing some glare which distracts from what would otherwise be a warm and reasonably smooth midrange. Others have commented that stock Marantz players do have glare. I have a disk on repeat to quickly break in the analog and digital outputs, and the glare seems less now, but if what I am hearing is characteristic of Marantz then I am comfortable with Paul's assertion.
By the way, I am quite sensitive to glare. For example, I was not satisfied with my Cary 303 as a standalone player because of glare and some HF hardness (it did make an excellent transport though!). I should also note that I have recently moved to a new home and have yet to put up acoustic treatments in the corners of my room, which in the past I have found to be very helpful at reducing HF echo/reflections.
I had exchanged emails with Paul and found him quite modest. In terms of performance when modded, he felt that the SA11 was a bit better than the SA14, which was in turn a good step ahead of the 2000ES, which was better than the 595. Note that there is a big jump in price from the 2000ES to the SA14 so build and parts quality must be a factor here.
What I like about TRL is that their mod has a more realistic and palatable price than other modders. It is less clear what exactly TRL does but maybe extensive / wholesale parts replacement is not necessarily critical? What is encouraging is that the owner of an APL modded 3910 (mods cost $3k) found the modded 595 to sound musical and engaging, though lacking in the last bit of detail and precision. If so, then it bodes well for what a TRL modded SA14 or SA11 would be capable of, but with the investment more on the underlying player than on the mod itself.