I'm looking for a good flash for my K10D. And I think I"ve decided on the Metz 54 MZ-4 series.

However, I noticed another version, called Metz 54 MZ-4i that's a lot more expensive (200-300).

However, I can't find any US dealers that carry them.

Does anyone know what's the difference?

I've heard that the i means it has new integration of the i-TTL to be used with new systems and very helpful. Is that true and worth that much more?

Thanks.