Sydney International arrivals and the domestic transfer area at the international terminal can be crazy in the early morning. You may have to wait quite some time to re-check your bags at the domestic transfer area unless you have OneWorld Sapphire or Emerald status and can use the business class check-in line. You will be unlikely to miss the connection due to the crowd/queue as they will call people to the front of the queue for flight that are getting close to departure. But it may affect your shower and domestic lounge plans.

I would be comfortable with a connection in that time range, but would also not be surprised to end up skipping the domestic lounge and shower plans if things are busy as the international arrivals formalities.