Great units but good luck getting on for $1k these are probably closer to $2k, maybe without data logging you could get it down the $1k. I have been looking into these for my IPRA car so have only really focused on the data logging versions.
There is a third version from race technologies called Dash 2 (UK company).
The haltech on is made by Racepak based out of the USA.
The EMS one is the AiM motorsport MXL, which comes in three versions (also USA based).

I am pretty sure there are no modification codes in QLD or NSW that cover instrument changes. You will still need to remain current with the ADR applicable to your model and year of manuafacture.
Doing a quick review I identified ADR 18 (applicable from 1 Jan 1973), ADR 18a (from 1 Jan 1981) and then ADR 18/03 (I think that was 2003). ADR 21 (from 1 Jan 1973) this is related to impact on dash, which should not be effected given there is a steering wheel between you and the dash.

http://www.infrastructure.gov.au/roads/motor/design/pdf/18.pdf

ADR 18 is the requirements for instrument layout. If you can demonstrate that your instruments comply with ADR 18 you should be ok. This also seems to imply you need to have at a minimum those instruments listed in category 1 and 2. There are additional rego requirements in each state that may effect you when you go to renew rego/ sell the car. In Vic there is a Vehicle inspection bulleting that requires all cars after a certain date of manufacture to have a speedo and Odometer but I couldn't find anything for NSW/QLD. I think prior to ADR 18 you didn't need to have anything on your dash not even a speedo.

Hope that helps

Bryan