Has anyone actually gone to gmx.com before? Seems like a very specific provider.

It's owned by 1&1 Mail & Media GmbH, which is a German internet provider.
Their head office is located at Brauerstr. 48, 76135 Karlsruhe, Germany.
On the same block as 1&1 is Taumi Karlsruhe Asia Fusion. It is the only Asian fusion restaurant in Karlsruhe.
On the menu is an item for 19.90 euro called Sake Tsunami featuring 8 parts Maki, 4 parts Nigiri and 2 parts Sashimi. There is no other menu in the world containing a food item called "Sake Tsunami" (Although there is a drink called "Sake Tsunami" from 49th State Brewing, which Alaska is the 49th state, probably nothing.)
On the cover of Satoshi Nakamoto's design book, "Wave and Ripple" is a picture of a tsunami.
Furthermore, Karlsruhe is only a 2 hour drive from Basel, Switzerland on the A5, Headquarters to the BIS (The central bank of central banks).

If you look closer to the fish servings:
>8 parts Maki
>4 parts Nigiri
>2 parts Sashimi
They half, like a bitcoin halving.

tl;dr: Satoshi is, or was, a German living in Karlsruhe.