To be honest, from the Dancing Galaxy and Another World sound, not to speak about more recent stuff, it seems like it was Yaniv Haviv the mastermind... But that's just my taste...
As for Koxbox in U-Turn the tracks where Ian joined were the best of the album IMO so it seems that he is quite needed.
And as for Serge well... it seems like he is quite the mastermind, judging from the inlay he did the most work for Delta Aquarids, and this album freaking roxx0r.
But look at Transmissions of JR. All the super stellar tracks were a collaboration with Stephane. And also Feel The Universe and perhaps more. So perhaps Total Eclipse was more than Serge and a true collaboration of masters after all...