Catman, you should try and see if you can get your hands on a Powell also. The Powell with a Nagahara or Williams head totally surpassed anything that I have ever tried, but of course that is my own personal preference and opinion.
I just bought a Nagahara head for mine and whoohh!!! It is killer! If the Nagahara heads are this amazing, I can only imagine what their flutes must be like!

I agree with Patrick. Just buy whatever you, personally, like the best. Someone will have something negative to say about whatever brand you pick.

Qualitywise, it is generally safe to purchase a flute made in Japan or Boston.