Anytime Grant. Yes, in my experience the Sig Plus seems to posess more natural treble extension (shimmer & decay on a cymbal hit, etc.) while overall being more neutral and not as "slightly dark" overall as the Signature model was in my experience. There is also improvements in lowered noise floor, extension in bass, dynamics, and to me the midrange seems to have more "purity" per se... perhaps the lack of "slightly darker" tonal balance that I thought the Sig. model had. As I mentioned above, Chris @ BPT will tell you if you call him, to try the amp plugged both into the amp duplex as well as the duplex next to it, as they both have different sonic characteristics.