Yes- the shelf is too small to stand the speaker up. The shelf (one of four compartments- a two by two grid) is about 18" wide by 8" high by about 20" deep. If I could have removed the divider between the two upper compartments, I would have put the larger center (about 8"tall 20"wide 10"deep) in that space. So, instead I'm currently using one MiniMon (about 12" tall, 8"wide, 10"deep) in one of the compartments and think I may try the other in the other compartment beside it.

With the 606, do you think it would be better to run two sets of cables (one to each speaker) from the 606's center output. Or, run one cable from the 606's center output to the center speaker 1 and then another cable from center speaker 1 to center speaker 2?