(couldn't help but notice this was your first post): since you're new, if you didn't know, stages can replace any stage desired, if they have the corresponding rel file set up in the module folder. Pretty much what I'm saying is that you shouldn't feel restricted to only have Temple stages over temple, etc. since a final destination one can replace it. Characters are different though.
As for music, I'd suggest one of the following to replace the main theme:Rozen SatoriMonster Hunter Tri Quest Complete
The results theme from Sonic Colors has good music too, but I can't find it on the vault.