My son has a k55 (prior model) that he has used many hours a day for years. I was surprised how well the keyboard held up.

I use a Lenovo y510p at work and home and after 2 years installed a new keyboard as the tops wore too much for my taste.

It appears Castle Crashers capped the frame rate at 30 so the 820m would be ok at that.

My vote is the 5th Gen i7 in the Lenovo.