there was only 1 volume released.
be aware though that the sound emulation for the genesis games is TERRIBLE i mean insultingly disgustingly bad, so any money you shell out will ultimately just be purchasing a copy of virtua cop 2 and sega swirl. while virtua cop 2 is the 2nd best light gun game for the dreamcast if you don't have a light gun sega swirl is not worth 10$