I have seen many, many forum posts by people who are collecting and re-painting Rogue Trader era figures. I can resist no longer.
I sourced some plastic 'beaky' marines on eBay. These weren't mint on the spruce, they were badly painted, badly glued and required considerable effort to clean up with some dettol and a sharp knife. As I was planning to convert them anyway this wasn't an issue and more importantly they were cheap.
I'd always been a fan of the Corvus marines but thought that the plastic kit marines were limited in the poses available and tended to look a little hunched over and ape-like.
I'm painting them as Imperial Fists and should have between 15-20 marines once they've all been cleaned and converted.