Perhaps, I have not fully appreciated Sigma lenses at this point in time with my Nikon D90 but there's nothing really to stop me from evaluating her top-of-the-line flash - Sigma EF-530DG Super?
Priced at a Nikon Speedlight SB-600, perhaps, its a value buy?
So, here it is, my next agenda to accomplish and share with all.
Check back soon.