Well Spintel is not very good for broadband, however it is ok for mobile (we have had experience with both).
They use Optus and at the moment this seems one the cheapest 6gb plan, without any lock in or special promotions.
You need to pay $10 for sim so first month is $49.99.
Also Iinet doing for same money 7gb but includes $300 international.
Another good Iinet deal is is $19.99/mth for 2GB and $400 calls/sms.
What's their support like?