You probably did not expect me to reply, but given that I have exactly the same username as your one, I am pretty sure you will do the same as I did:
1. Contact Chris Nachtrieb from Chris Coffee Services and find out that Quick Mill Alexia is much better than Isomac Zaffiro (which cannot be PIDed, at least officially), and that Alexia is the model which was created by Quick Mill in collaboration with himself. But it all does not matter - you cannot get espresso machines from US.
2. Contact Coffee-A-Roma and find out that although normally they do not sell Quick Mill Alexia (only Andreja), they can get one for you, but in its standard configuration only.
3. Contact Quick Mill asking about what is the difference between standard Alexia and the one sold by Chris in suspicion they are the same. You can still suspect that - there will be no reply from them. Parla solo italiano?
4. Contact some other overseas online shops and find out the same old story - they do not deliver to Australia.
5. Start suspecting single boiler machines have some significant limitations and check other options (HXs and double boilers). Get more information and forget about the price for a while.
6. Visit Talk Coffee website and check different machines. Pay attention at Giove II.
7. Search more information on this site and find comprehensive thread started by tashie and called Giove II / TCI - many thanks to tashie and to all those people who replied him. Sorry, I am not allowed to insert links yet.
8. Contact Chris from Talk Coffee and visit his showroom - he will give you generous tour with detailed technical explanations.
9. Figure out that single boiler is not an option even for ristretto drinker - you are not that rich to buy cheaper stuff. I am pretty sure that the first time you make a milkshake (and you will have to do that sooner or later) you will hate yourself for that you did not buy double boiler straightaway. Yes, it is more expensive, but single boiler with PID will cost you roughly around $2,000, and you will not be happy to pay such amount of money and keep always in mind and doing all precautions when switching from boiler to steamer and back and waiting. Roughly the same applies to HX (and with HX you will also be very limited in changing temperature on your PID, which will be acting as pressurestat rather than temperature control device).
10. Have a look at Giove II (double boiler with PID) and buy it. It is made by CBC Royal First, which seems to be an offspring of BFC (the one which makes Diadema), at least it is located in the same town and literally next door.
11. Pay attention at the main disadvantage of Giove II: you cannot plumb it into the water supply (but at least Giove II i safe - it has water level control and will shut off automatically when the water runs out). But most likely, you will use water, which is filtered separately, and wont need to make a lot of cups at once. This assumption might be wrong, and thats why it is worth mentioning. But if you want ability of plumbing (hence rotary pump), you have to be prepared to pay another extra $750+ and get much wider Izzo Alex Duetto II. It is beautiful machine, but dont forget that your primary goal is double espresso/ristretto quality, and the difference to Giove II (and to many other similar machines) in this area will be minimal. Your key criteria are simple: double espresso/ristretto quality, device safety and ease of use.
12. The last, but not the least: buy naked portafilter. You have to explore what it can give you.
13. And finally, wait for about a month to get your dream machine - its Christmas mate. And you are more busy, than eager to get your dream machine and bring it to your place immediately!