Dear darren: I understand you and for the most part I agree with you, let me to explain a little about synergy from my point of view ( that it is only that a point of view and not in any absolute terms. ): I can't comment on your SPU example because I don't know the history behind that design and I don't have yet the opportunity to try it in my today audio system.
When you speak of the PC-1 or XV-1 trying to match to a Phonolinepreamp my point of view is that if one of these cartridges ( or both ) needs a special sound " signature " in a Phonolinepreamp to performs at its best this means to me that something could be wrong around those audio items: if the Phonolinepreamp is an accurate/low distortions ( not analytical ) ( no colorations ) design then the cartridge has a little problem ( assuming good tonearm match and right set-up and loading. ) and that cartridge is not up to the task and of course things can be on reverse too when the Phonolinepreamp is full of distortions/colorations/inaccuracies, in both cases there is no synergy.
Darren, if you take a look to the Agon second hand audio item ads you can make a question: why so many and different ( almost new/mint ) audio items for sale? what's wrong?: well maybe many of those persons are looking for synergy and they don't find it yet and IMHO they don't find it yet because what almost all are doing is to buy/try audio items that are compensating the errors of some audio items in their audio systems and with this compensation they think they can achieve that critical and elusive SYNERGY but sooner or latter this kind of " audio attitude " show the " cooper " because the sum/add of two errors ( IMHO ) in my audio experiences almost never give you the right/correct and precise performances.
Do you know how many years that I don't buy audio items like: speakers, amplifiers, phono stage, line preamp, etc, etc ?, too many to remember and why is this?, very simple: I already achieve TRUE SYNERGY through my different audio items where I was and am looking for that true-synergy where I don't have to compensate for anything anymore.
Stay where I'm take me not only a lot of years but a lot of real time testing/trying/changing/etc but the reward is worth any effort on that direction.
Do you think that you already achieve in your system TRUE/REAL Synergy?, I know the answer because I know every single audio item in your system ( but the phono stage ) and I know that you don't have electrical synergy ( example ) between the Wilsons and the VTLs because of its impedances.
Now, I'm convinced that people like you, me and several other ones agree in 80%-90% what must be the quality performance that we are looking in our home music sound reproduction systems, we almost all have more coincident " attitude " about that differences.
I know that nothing is perfect but beyond your opinion, mine or any one else: my quest is for be near that " perfection " and I have to say that I don't accept ( normally ) nothing less, this is the main reason why we design/build the Essential Phonolinepreamp and that's why I have my " old " system running with out the normal tendency to change it.
Anyway, I think that we are talking almost on the same subject SYNERGY but the point is that I speak on true/real synergy and till you achieve it or be near it it will be difficult to understand at 100%.
Regards and enjoy the music.
raul.