Thanks @Jzad and @NWT.Stuff really helpful thanks for spending time to reply.
These are really 3 separate UNCOVERED areas that need coverage with one audio source rather than zones that need to have different audio feeds. For ease I am actually thinking of dropping this to two areas using only 4 speakers. I presume if I did this the amplifier would cope better?
We live on top of the Pennine Hills in the UK so we do get some pretty brutal weather - which was why I was considering the Polks as they had a good combination of audio quality and resilience.
@NWT.Stuff I did think about the Herdio speakers, but TBH they seemed to get bad reviews for longevity (i.e. rusting) BTW great Nobby Box project!
@Jzad I am happy to go with used gear and I would consider using the Arylic receiver with another amps and speakers. The maximum speakers distance from the amp is about 7m ( I am planning to put the amp in a waterproof wall mounted box).
Area 1 is an outside dining table (with the mounting point for the speakers about 3 m away from the table)
Area2 is the hot tub/ decking area ( this was going to be 2 areas originally). The Hot tub and decking area is about (7m x 7m). I was going to put the sub in a central area near the amp which I was thinking would bolster both areas (which are being fed the same music)
I didn’t want to go for much bigger speakers than the Polk Atrium 4’s as I wanted them to be more discrete (hence the thought of the subwoofer) but we could go up slightly in speaker size I suppose.