Isn't this type of thing more likely to be what football manager is about though, i.e. number crunching, you said yourself that it doesn't need the 3d gfx and from what i have seen it, the game, uses as many cores as it can get its mits on if you enable "threading" from the in game options.
At the end of the day i am playing devils advocate a bit, i liked the 620 i had and seriously recommend it IF you want a
guarenteed 4 cores, and
tbh from what you say it will be used for and what i have seen comparing the 2 chips, and you admit to too, if the 550 you get doesn't unlock to a quad you may well lose some performance in that particular game.
Might be worth getting one of those mobo's that allow unlocking of seperate cores if you are dead set on a 550, turn a dual into a triple if one core is fubar, was it asus bioses that allowed that?