Ground wire


I using the iotavx sa3/pa3 paired togther.  The sa3 has one ground thumb screw, located on the back panel. How much gear can I put on that one ground screw if need be? I will be getting a turntable and 2 rel t5i subs soon and although I don't know yet if I will need to use the ground wire on the subs for high connection... I really don't know if it's cool to put three or more on the ground screw of the sa3.  If it's ok... is there a way to do it? If I need to ground the two subs... would I just twist the two togther? If I connect the turntable.. can it touch the ground wires from other gear on that screw? 
Thank you.  :)
tmac1700
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Remember, only one source is used at a time, I leave other source devices off, then a gazillion wires can go to 1 ground point.

I have had to extend ground wire of din cable to reach ground screw at far end of the preamp.

I have 3 tonearm ground wires to my SUT's 1 ground connection.

If some ground wires don't reach, you could make a ground substation, i.e. ground hub, then 1 wire to the ground terminal. Insulate the hub of course. 
Thanks fellas.. I appreciate your replies.  
REL doesn't think I'll need it for the subs as well but they mentioned it incase I do get a hum... so that's what got me thinking about it.