Australia has become SO competitive for solar and battery installation you can actually be fairly safe nowadays just picking any old supplier that has >4.7* on google and there'll almost definitely be <10% price difference (that's the WA experience anyway).

Going with a door knocking sales rep for home batteries would be madness in most countries but chances are pretty good that in Australia you would get a perfectly decent product.

In place where I live you do that and they will rip you off good time.

Better to DIY or at least do really good market research first.