I use both a Razer Naga
and a Razer Nostromo
. The Nostromo looks just like a Tartarus, but I have no idea what makes them different...
*I took a look, the keys are "soft" on the tartarus and the #15 button is moved. 15 on a Nostromo is a large button under the D-pad. Also it looks like the D-Pad on a tartarus is like a joystick. On a nostromo you have the option to remove the nub and it just be a d-pad (I did not like the nub)* I'd maybe go with a Nostromo...
I do not use the D-Pad for movement, as it never felt right. I use "2,7,8.9" for WASD movement. The "down" button (on mine, down is left, because the d-pad is rotated for your thumb's natural placement) is my "3", the Left button is my Push to Talk for Vent/Mumble and I have no idea what I use up and right for off the top of my head (maybe nothing).
The "15" on my Nostromo is Space, so Jump.
Toss is the Naga, and I only touch the keyboard to type.