My understanding is that GYM has some inherent limitations that will always cause it to be inaccurate on some soundtracks regardless of the emulation accuracy (in particular ISTR reading that its YM2610 register emulation is only frame-accurate). As I recall, the developers behind the VGM format have laid the groundwork for better Genesis logging support, but last time I checked there was no user-friendly way to rip a Genesis VGM. In any case, would switching SX's archive to GYM provide anything that, say, Zophar's Domain doesn't already provide?