Just got a block plane from Lowes (the only one on the display). It has a cup on its sole. Is it supposed to be like that?
Take it back. The bottom of the plane should be totally flat within the reasonable ability to measure flatness.
Most hand planes you buy unless you get a premium hand plane you need to tune. There are several tutorials online on how to do that. http://www.instructables.com/id/Tuning-a-Hand-Plane/
I normally take plane apart and flatten the sole using a granite stone using higher number wet sandpaper, the water will keep the paper sticking to stone.
You can use a permanent marker on sole and when lines disappear your sole is flat.
You should also flatten the back of your blade using same technique.
To get proper bevel I prefer this tool.
I hope this will explain it in more detail.
Now this takes time but the rewards comes when your tool works as it should and you get crisp cuts each time.