Doitsu scaled Koi are commonly bred and very popular with many Koi keepers, Armour scaled are a different subject.
Look at some pictures of a nice Shusui and you'll see well placed large "doitsu" scale patterning. I recommend Shusui as the color patterning makes the scale placement stand out well.
Armour scales are messy, random, and not considered desireable (except among a few lonfin breeders who jack up the prices as though they were "special") In a way they are special... Kind of like the Koi worlds equivalent of riding on the short bus to school...

(sorry to be so tacky)
As for your yamabuki, it is hard to tell how it may go. The body is filling in well, the color is pretty decent, and the dark patch on the head is fairly common, especially on young koi. Good color in the pond.
As already mentioned, there are several good domestic breeders around as well as Maurice in the UK. You won't find any Aussie Koi available for import as they have had stringent import/export restrictions in place for years which has hurt the quality of their domestics for the most part.
Since you are working with a thin wallet (I can identify with that

) good domestics will yeild you more bang for the budget buck. MOST of the inexpensive Japanese imports are culls and it takes a very practiced eye to find gold in a lead mine. We obviously have some very good importers who advertise on this forum, and I wouldn't hesitate to do business with any of them, but their good imports are going to cost you a lot more than what you've been paying... You will also be getting a huge difference in quality to go along with the price tag.
Breeders in the US like Matt, Brady, Brett, Richard, are producing some very nice Koi at much more reasonable prices and they will shoot straight with you about what you are getting. THAT is important when buying better Koi. An honest relationship with your source.