Adding an electrical outlet

[oldelmer1]

I, well, DW, would like me to add an outlet in the kitchen right behind the sink. There is already an outlet in the corner of the L where counter turns 90 degrees away from the outside wall. So I think all I need to do is tap off this outlet and run it over behind the sink.

My question is, since this outlet is below the sink, should I install a GFI outlet there? I know all the outlets are fed from GFI to begin with, but just wondering if another GFI would be better.

Thanks.....