SunflowerZZ,
Besides the motor, the motor pully, the size and weight of the hand wheel will make a big difference in how a machine sews.
A larger amp motor won't necessarily make it sew better. I've switched a bunch of them around and they all sew about the same. You can try it on your machine and then tell us what happened.
I do know that my wife's 319 sews through multiple layers of denim without a problem. And it's box stock.
Joe