Hi @Amphicar770
We don’t have Axitec or Certainteed panels over here, so I can’t comment on them. I think SolarEdge is a perfectly good alternative to Enphase though.
Sunpower, REC, Enphase and SolarEdge are all great products, I wouldn’t worry too much about splitting the difference between them.
18kW is a very large system by Australian standards, is that what you need to cover your household usage? If the upfront cost is an issue, it may be worth looking at your consumption to see if you can get that lower as a starting point.
Cheers
Marty