Well, it might help to listen to some guys who have actually recorded guitar with a symphony - how Metallica's rhythm tone changed between the studio cuts and their symphony album, Steve Vai's work with a full symphony, Yngwie's concerto suite...
Likewise, a lot of Dream Theater is quite symphonic, and I think it made JP's first G3 tone very striking in that respect - Vai and Satriani had these very broad, wide-sounding guitar tones, while JP's was very focused. This was ages and ages ago, 2001 I think, but at the time my response was, well, first that his tone kicked ass, and that second you could totally tell that he spent most of his time playing with a keyboardist whereas Vai and Satch played solo material. It was much more focused sounding than their tones, designed to cut where it needed to but not do much else. The bass was dialed back quite a bit,a nd the low-mids sounded scooped. Meanwhile, it was a Mark-IIC+, so it didn't have a Rectifier-like treble crunch, either.
Finally, when in doubt, spin some Porcupine Tree.
