There are certainly players in the Eredivisie that can do a good job in the Premier League but Manchester United is if you are honest one of the best clubs in the world. I don't think he is capable enough for such a club. Can't think of anyone in the dutch Eredvisie who is capable for such a club.
Both Vermaelen and Vertonghen have their good games at Ajax but they're way to precarious (think that's the word) for a topclub. Certainly good players for Ajax or clubs like West Ham, Newcastle, Fulham... But I don't think they can handle the absolute top. (Not yet, maybe over a few years)
Dembele, Schaars, Affelay are players that I would definitely take a look at if I were Moyes. Maybe also Suarez if it's got to be an amsterdammer