I always liked Melinda. It's light and pretty but not frilly, and everybody can say and spell it.
My best friend is named Melinda Erin. She's called Mindy for short. I don't know too many Melindas that aren't Mindy.
Of your combos, the only one I like is Melinda Opal. Most are just too heavy on the syllables, and the middle names seem like they're overcompensating for Melinda not being "classic" or something.