Akirus, I'd definitely go ANU for physics. It is, by far and a mile, better than Monash for undergraduate teaching and research. Take it from me... I'm going to the United Kingdom to close out my Physics major (Univ. of Nottingham). I, too, was frustrated by their lack of advanced topics and will be studying chaos theory and general relativity (both not offered at Monash) as part of my major, there. ANU has even more units on offer, as I'm sure you've seen.
Also, the best way to get in on good research at ANU is to come through their own ranks, impress the faculty members there in undergrad and you'll have no shortage of offers to continue into postgrad.
It's harder when you're a grad from an outside university. So yes, whilst you may be able to save a year doing sci scholars program at Monash, you may lose more than 2 years attempting to get into ANU where the real theoretical physics research is taking place.
In my opinion, aim for a PhB at ANU. Yeah, the move would suck at first, but if it's your dream, you should definitely go after it