[DaveX]

If I were to add a subwoofer to the D200's.

The speaker cable is 3 core (L/R + ground) am I right in saying that you would only ground one D200.

And using 2 subwoofers (one on each amp) you would twist the L/R wires together.

Thanks.

[CIAudio]

If I were to add a subwoofer to the D200's.

The speaker cable is 3 core (L/R + ground) am I right in saying that you would only ground one D200.

And using 2 subwoofers (one on each amp) you would twist the L/R wires together.

For a single subwoofer, you will use L+, R+, and - from either amp (ground is common).

For two subs, use L+ and L- for one, and R+ and R- for the other.
Never tie L+ and R+ together, this will destroy the amplifier.

[DaveX]

Never tie L+ and R+ together, this will destroy the amplifier.

I meant if I twist the L/R (white/red) wires of the 3 core cable together this would give me one + channel and the third wire would be the - ground.

[CIAudio]

I meant if I twist the L/R (white/red) wires of the 3 core cable together this would give me one + channel and the third wire would be the - ground.
 

I'd ask the sub manufacturer regarding the above...
It also depends on if you want separate L and R woofers, or two mono's.
There are probably a few ways you can wire them.