Best Characters to Build?

So I'm reaching my deck limit. And because research times are so long, I just can't figure out who to focus on and who to recycle. For Epic cards I've currently got Bob, Peggy and Stan in my deck. And they're all pretty awesome. I've also got Bill and Hank who do have a few good combos. That said, I just spent days researching Louise only to realize she's not that great a card. Just meh. Who to focus on? Epics - Amy, Boomhauer, Brian, Francine, Leela, or Stewie? And any powerhouse Rare characters worth building?

I've got basically one of each "type" card - music/school/costume/art - in Epic or Rare, and lots of various alcohol cards. So who are the top dogs and who are the bench warmers?