I am planning to buy an external flash.
I did several searches about nikon speedlights and made comparisons.
I was using 540fgz when I had a pentax system.
I liked the size and GN of SB800.
Newer models, SB910-900 looks bigger and heavier, the reason should be zoom range I think.
Generally I dont prefer 3rd party flash equipment, but if you strongly suggest a model ( I guess it would probably be Metz), I will take it in account.