Would also recommend getting quotes from at least 3 companies. Are these both from the same company? Try local electricians too, checkout our Solar Installers Sydney page.
I would not be pressured by the “price valid for 1 week only”. Take your time to decide and make sure you’re comfortable with the company you go with. A good solar company is probably more important than any other consideration when buying solar. They are your point of call if anything goes wrong. A quality installation regardless of the products is very important too.
You are right to beware of sharks, but if you take your time you’ll find some safe water.