Just leave any System Channels, System IOSes (including cIOSes, above slot 200), MIOS, BC, EULA, Region Select & The Homebrew Channel alone and delete anything that shouldn't even be there in the first place (trust me, you'll know when you see it).
Although... I'd recommend doing a System Check first though (using SysCheck), before doing anything else.
Although... I'd recommend doing a System Check first though (using SysCheck), before doing anything else.