These can't be run in series/parallel. The voice coils all have to be paralleled and the sensing coils all have to be in series.
The 16 ohm drivers have a DCR in the 13.5 to 14 ohm range so you can only parallel three of them.
I think the 370 watt amp is plenty for the three of them in the free air application. 600 might be enough to bottom them out so you'd have headroom but would have to use restraint.
