okay, so it's been a week and I've not managed to test those slave speakers yet. I'll try and do it this weekend.

What I did do however was remove the older teac system connected to my computer and replace it with the 568 and 3xdsp33's all configured in a line nicely and it was sounding pretty good.

then tonight the 568 will no-longer power on! I see there are 2 fuses in a little tray by the power socket, and if my little understanding of a multimeter is right, then I think one is broken. I can't see the break, but it doesn't seem to be showing continuity. I guess I'll be visiting maplins tomorrow... would they have the right thing?

Not sure why it would have blown a fuse mind..

Lounge: LG 55B6v, Some Denon receiver, Anthony Gallo Reference AV mains, Totem Dreamcatcher centre, SVS PC-4000, AppleTV4K
Office: Audioquest Dragonfly, Cyrus 6DAC, Monitor Audio CPW Gold
Headphones: NuForce HDP, Audeze LCD-2, Sennheiser HD6XX, B&O H6mk2