You're not alone...I, too, like the name Megan. Of your combos, I like:
Megan Caroline
Megan Elise
Megan Hannah
Megan Julia
Megan Michelle
Megan Olivia
Some other suggestions that come to mind at the moment:
Megan Alexandra
Megan Aurora
Megan Cecilia
Megan Cristina
Megan Daniela
Megan Dahlia
Megan Elisabeth
Megan Eliana
Megan Isabela / Isabella
Megan Liliana
Megan Leila
Megan Marie
Megan Maria
Megan Martina
Megan Natalia
Megan Noelia
Megan Ophelia
Megan Rebecca
Megan Sofia / Sophia
Megan Scarlett
Megan Samantha
Megan Tatiana
Megan Victoria