Actually there's another reason why you'd want the Jap voices - the English speaking voice actors in this translation have all the acting skill of a Primary School drama class. They're beyond awful. Normally I put up with it but this was just some of the worst voice acting I've heard sinse Resident Evil. I had to turn the voice volume down so I could take the game seriously.
The clips are there, btw, but the Japanese language option is gone! Well, I guess the gameplay's still the same.

Otherwise, some cheats I bled from Atari Australia:
Cheat Start - Y1B1R1Y1B1R1
PC Mode - B1R2Y1 (haven't got working yet)
PS2 Mode - B1R1Y2
Some of the original clips: (I assume?)
Original Animation Opening - R1B1R1
The Great Vortex disappears and the Romun fleet enters - animation - B1R1Y1R2Y1B3
Romun fleet destroyed - animation - B1R1Y1R2Y1R3
Napishtim destroyed - animation - No subtitles - B1Y2R1Y1
Ending - animation - No subtitles - B2R1Y1R2Y1B1R1
Not all the cheats I admit - there's a fair whack of those in different subitles and the cgi stuff Konami decided to add, as well as the usual "become an immortal super megagod with fireballs shooting out of rectum" style cheats, but I'm not interested in them.
Anyways, thanks for the help.