Nice looking project dude!
Don't get dedicated 4 way controls. Just use the 8 way. Most of the controlers have a plate at the bottom of them, that can make them 8,4 and 2 way.
FYI: You can get joysticks with buttons on the top of the stick. This is great for defender type games. You can get the from LAI Leasure and Allied Industries, they make joysticks in OZ.
Also space your buttons out a little more (they look a little to close), use your hand as a guide. As you will be the one playing it.
BTW: I used to make these
I'm sort of working on building a table top with a flat screen, as my first one was a little too big.