XZ1 + A3 printing

A3 is roughly 11.7" by 16.6". Which is about 3 times linearly the size of 4x6". You can try printing a 4x6 with a resolution of 1200x800 and see if the resolution is acceptable to you. I would say "barely".

Having said that, it depends a lot on the printing technology and also overall sharpness of the photo. Just because a camera has 20MP does not mean it actually able to resolve that much. XZ-1 has a sharp lens and that along is much better than most DSLR kit lens.