I know that at Mojo's, we are unable to daisy chain as the input impedance on the 600 is too high and we are not able to run the second sub at equal SPL due to the cut down signal. Knowing this, I would go for the Y-splitter at the receiver,

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70