1. You can sound proof the doors (with those expensive stick on rubber film thingy)
2. Choose tyres that's more suited to Aussie roads (Michelin and Continental's have horrible road roar)

BUT, most of the NVH is from the engine, the K24 is.... rather highly tuned to haul this bulk, the stock 5speed auto isn't helping. That's why other European Marque's are starting to use small capacity low-pressure forced induction engines in cars like new Volvo's Audi's VW's and Peugeot, because of the power delivery and the fact it'll be quieter.

Not much you can do about that sadly, maybe except try around different engine oils or something, the noise level of my CL9 is better after a service with decent full-syn oil.