Thank you so much for your prompt reply.
The local electrical /supplier/ installer who provided the quote is very reputable, and very pleasant to deal with. So I have no issues on that front.
The $6,600 quote of LONGI 300W MONO PERC panels , plus the Fronius Inverter 5Kw, included GST, and was after deduction of the subsidy. SO it appears not too bad at all.
Due to slight early morning shading on four of the panels, my installer recommended providing four TIGO OPTIMISERS only, at around and additional $80 each.
As I am a mature age technology and data enthusiast , he has also suggested an optional Fronius Smart Meter ( single phase) at around $490, should I wish to indulge myself.
In addition to LONGI, this supplier also provides panels from several other manufacturers including Risen, Jinko, Trina, Seraphim, REC and LG.
He seemed to like the LONGI MONO (better than split cell?) panels for my system.