Ah, either Optus or Telstra can provide you with this.
Optus Cable:
# Has 12gb unlimited;
Will reduce your speed down to nearly unsurfable speeds after this.
Telstra Cable:
# Has 10gb unlimited;
# Is a little more lenient and you can go a bit further over the limit without the cap;
# However once capped, speeds are faster than Optus, but still horrible.
It may also depend on your area. Some areas are only servicable by one Cable provider or another.
However, if you want max downloads and not that worried about speed - I suggest ADSL, as I'm sure the others here would agree. You can get a lot more (albiet it takes longer) in a month than on Cable. I'm not sure how much ADSL costs compared to Cable though, or know what plans you can get with it.
But if you want to go for Cable, above are your debatably best picks =)