Don't forget, you can put Anthrax in Harmonia as well for a very nice performance boost as well.
Midnight is pre-tweaked for all out speed, Harmonia tries to strike a balance between compatibility, performance, and battery life, but leaves the door open for customization. My personal setup is Harmonia 3.17 with Anthrax, not because of speed (things run fine) but because with this combination, USB OTG works, allowing me to connect hard drives and such for work.
Don't be afraid to try various roms as well as various rom/kernel combinations to find what best suits you.