As someone who has spent a lot of time in Mandurah but lives abroad, my biggest regret is that for too long I was completely unaware of Seven Trees. Sure, there are nice cafes in the Mandurah area where you can enjoy a really good espresso drink made by a skilful barista, but to be able to combine delicious in-cafe coffee drinks with the purchase of expertly-roasted beans for your home coffee-maker there is nowhere better than Seven Trees, a delightful family business. The packed carpark in the morning testifies to this but try it yourself. Gilbert's also sells many of the beans.
I have tried many of the range and never been disappointed. On my first visit I was actually given a tasting of 4 different beans and roasts each of which was delightful in its own way (amazingly, I slept just fine). I tend to prefer the darker roasts but that is just me and there is a spectrum to enjoy. If you are ordering overseas delivery as I do then my experience is that this team is great. Delivery is swift via Aus Post and you get what you order.
Kook in Barrel has a strong but refined taste and it's a variety I really enjoy.