I was thinking the same thing Dave. However, if you check the product page for the 350, the picture of the back does not appear to have a ground screw.

Also, to the poster, what type of cable are you using to the sub?

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85