Hi Burkuagh,
Firebird's soundsets are indeed presets only. It's different with Gladiator expansions, which have new features/waves next to the presets. So:
Firebird soundsets - presets only
Gladiator expansions - presets, new features & sometimes new waveforms
Gladiator soundsets - presets only
Expansion = soundset + additional features
Cheers,
-Bastiaan-