I think you probably should just make friends with your neighbour.
The M60's come with both carpet (metal) spikes and with rubber feet. You'd obviously want to use the rubber feet on hardwood floor.
But the sound transmission from your unit to your neighbour is a function of vibration and air leaks between the units, not necessarily of the quality of the speaker. Lower frequencies are going to carry more, but the M60 model is not necessarily going to make your neighbour situation worse.
Rugs might help. But I'm going to seriously suggest bribery.
