Connecting an Avantis SLink port to a gigaACE card in a dLive DM MixRack will give you a 128x128ch link but no Ethernet tunnelling and no control of the DM preamps from the Avantis.
With two gigaACE cards (one in the Avantis, one in the DM MixRack) you would get a 128x128ch link AND Ethernet tunnelling, but still no control of the DM preamps from the Avantis.