Hi @stich
You can check out our Solar Power Sydney page, we’ve got a few installers listed on there.
In answer to question 3, yes. There are significant differences in the technology and often quality of panels. Whether it’s worth paying more for top range gear vs mid range, that’s a personal preference (although it’s definitely not worth getting cheap gear).
The below chapter in our Solar Guide will help you navigate those questions, and also have links to the panels and inverters that we recommend, which is up to date.
https://forum.cleanenergyreviews.info/t/ch-6-what-panel-and-inverter-brands-should-i-buy/159/1
Cheers
Marty