Get the asrock mobo. And don't worry your e7400 is good enough and it will NOT bottleneck a card like the 6770.
Bottleneck is not all about cpu, it about games. If games require more cpu power, then e7400 is poor for modern games, like witcher 2/skyrim etc. Bottleneck totally depend on games, how much cpu power they need. And most of the games are cpu intensive and will bottleneck on e7400.