Estuary fishing in Perth is what anyone from SEQ could describe as limited at best. I took my 4.5 centre console and pretty much spent most of my time over there wishing I had sold it and bought something bigger over there. That said, at the time (nearly 15 years ago) the crabbing around Mandurah and the sqidding in Cockburn Sound were some of the best I have ever experienced. Since then W.A. has not only introduced a fishing license but massively clamped down on bag limits. If you are a catch and release fisho - all good, If you fish for a feed - suggest looking at the regs for your zone before you shell out for a new boat. The wind over there is bloody incessant and sheltered water is not something there is an over abundance of. The distances required for offshore combined with the usual sea conditions realistically set a minimum size boat at about 5.5 metres in my mind unless you are happy catching bream and blowies and blowies and blowies. Did I mention the blowies - bloody toadfish in the river are as incessant as the wind. Soft plastics are almost financially unviable. Point being - if you haven't spent time fishing there already, it may be worth holding off until you have spent a bit of time there. Do a few charters and a heap of research on the actual fishing as your requirements as you see them now may well change.