Let's not forget the dungeon tracks either. Two particularly awesome ones are The Withered Forest for the 4th Stratum, and the 5th Stratum Music. (The name is a spoiler.)
Even the event music is awesome. Ladies and gentlemen, Blue and White.
The battle theme of the 6th stratum Ecstasy ,considering that it's the battle music that only plays in the Bonus Dungeon of an already Nintendo Hard game, the only thing matching it's awesomeness is the difficulty.
I won't spoil where this theme is from, but Rising Again sums up the battle it is in perfectly.
Taken from the 'Live Music by Piano and Strings: Sekaiju no Meikyu I & II Super Arrange Version' album, we have excellent remixes of Cherry Tree Bridge and Blue and White