Okay, now we may be getting somewhere. Thanks for the update.
As to the noise between tracks, that probably has to do with the Para's internal DAC's shutting off and turning back on. Some cd / dvd players actually turn off the digital output when no signal is present. This causes the DAC to go out of lock or temporarily shut down. When the next cut starts up, the digital datastream is re-energized causing the DAC to switch back on.
The "cure" for this is to have the Para modified so that the DAC's don't shut off. I know that this can be done as i and many others ran into this problem when CAL went to their 24/96 versions of the Alpha and Sigma. All you had to do was to disable a transistor ( probably being used as an electronic switch ) and there was no more "clicking".
Another solution to that would be to change the digital transport that you are using to something that outputs a continual digital stream. This would allow the Para's DAC to remain in lock. I don't know if you would run into this problem when running optical, but that is a moot point since your current DVD doesnt' offer that type of jack anyhow.
As to the "digital noise" that becomes apparent as listening levels are cranked, have you ever adjusted the digital input trimmer ? I ran into something similar with my 1800 when i had it and i had to knock down the drive level coming into the processor from the DVD player to correct it. While this wasn't a problem on every disc, it was quite apparent on some that were recorded a little hotter than most. The higher recording level resulted in higher output levels from the transport which drove the DAC's into digital clipping. You should be able to find info in your Para manual about how to correct this problem if you already haven't looked into this. Why this would be apparent at higher volumes as compared to lower volumes simply has to do with the fact that you can more easily hear the noise / distortion that it is generating.
These are both just guesses, but i hope that they might at least point you in a direction that goes somewhere... Sean