There was most deinitely a problem with daisy chaining the EP600 when Mojo and I were doing the sub comparisons. It was thought that the latest batch of amps with the higher filter(150hz) on it and no by-pass mode solved the issue, IIRC. I seem to remember a couple of posts by a few owners with the newer amp design and they were able to daisy chain the 600 without the drop out of the other subs.

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