The M3 may fit, but I seriously doubt it would power a system based on the hardware you're looking at. A suitable PSU would have to be outside the case.
In addition, you're looking at an Intel Core iX CPU, which will need CPU cooling that will likely not fit vertically in the M350 case. From what you say, you may very well have done a test fit with the CPU cooler, so this may be a moot point.
Either way, you're looking at a PSU that will not fit in your M350 case.
When choosing a PSU, I would recommend looking primarily at functionality, and form as a secondary criteria.