Thanks for the heads up about the 1U standards :).

I think I'll start with a Metropolis+Atlantis+stereo line out 1U in a 104hp 7U case and play with that. After that maybe a Maths or a reverb, no rush to decide.

The Atlantis sounds nicer to me than the Mother on the audio I've listened to, and the Metropolis looks like soooo much fun.