Running Back/Flex Dilemma

Can I get some opinions on this?

I've got five running backs and they all seem to have good match-ups:

Reggie Bush/Buffalo
Beanie Wells/Cleveland
Cedric Benson/St. Louis
Felix Jones/Tampa Bay
Kevin Smith/Oakland (assuming he's healthy)

I've pretty much decided my starting receivers are going to be Hakeem Nicks and either Torrey Smith or Laurent Robinson (I also have Crabtree and David Nelson, but the former has a bad match-up and the latter hasn't been putting up great numbers.)

I need to decide on my two running back starters, which second receiver to start of Smith and Robinson and who to put in the flex. Any thoughts?