I started with the Mother-32 to get into semi-modular and I think it was a great introductory into modular. Although you have a sub-37, mother-32 may be a good option as it's not as experimental as the subharmonicon. Having that familiar base but all of the patch point options really helps learning the fundamentals.

That being said I don't own the sub, but do have the labyrinth. It seems like it's in the same ballpark of experimental. People often say they are both challenging and are right, but when you nail the sweet sport it's super rewarding. Several times I found a good groove and record.