I agree on just keeping it as a 4-way. From what I recall most joysticks can be switched to be 4 or 8 way by just flipping the plastic cone thingy at the bottom, correct?
I suggest try with a 4 way, if you don't like the performance, then switch to 8 way and then see how it is a pain on the 4 way games.....
Also, I wouldn't even bother with any of the trackball or spinner games if you only have a joystick.