Australia seems to have a rather expensive take at boats. You might be advised to investigate the cost of importing from the States or
Panama (where cruising dreams get divorced, alas) if you are wishing to move up. I am just over six feet but when I got my seven foot clearance
steel cutter, I found it very liberating as it seemed and continues to seem very airy and spacious above my
head. In fact, it's more
head room than my basement.
That said,
headroom is only part of the puzzle. Were I to
cruise distances, stowage and tankage would trump a bit of crouching, and were I to weekend out of
Sydney, say, to cruising grounds 100 NM or less away, with plenty of boozing guests and noshing relatives, I would opt for a standard issue French-type cruiser, because they go fast and "play nicely" for the social activities, even as I think they aren't ideal for
offshore.
So, the constant in boats is "everything is a compromise". I know a couple where BOTH the man and the woman are about six-two in height and they do well on a Niagara 35, about the smallest size I would take offshore. But it's what they could afford and what they could (easily, given their inherent strength) single-hand on
passage.
I considered a 45 footer, but bought a 41 footer, because my wife is relatively runty and could only
work that size of winches and running
rigging. Thinking in terms of "I've been up in this gale for 24 hours and I have to leave my wife in charge while I do a coma sleep" will dictate your choices ... which is exactly where the "sail the smallest boat you can stand" attitude comes from.
Good luck and shop BROADLY. Australian prices are not good from what I can see.