To all the bros with sexless marriages, sorry to hear about your predicament. It does feel like you're doing it all for nothing, especially if you're a punter as well. Then your mind starts to think "why go through all that trouble when I can just pay for it?".
It could be sexless because you no longer find your wife attractive or she has become uninterested (but you still have the desire to fuck her). If it is the latter, you can do something about it. Use meds to improve your performance in bed and get her interested again. Work on your self-image, etc. If the reason is the other one, then it will be very difficult to fix because it can only be fixed by her. Would she hit the gym and get fit, just to present you with a more fuckable wife? Not very likely.
Anyway, if divorce is the only solution, you're probably going to need some facts about divorce law in Australia before you pull the trigger.
I think the most important fact is "No fault" divorce is used here. What it means is, when it comes to how the courts process a divorce, it does not matter why or how the divorce happened. All divorces are processed in the same way, taking into account the same factors. Think long and hard about this because it could play out very differently from what you expect.
Take 2 examples. First example, a high-earning high net worth man divorces his highly promiscuous, cheating wife with all the evidence to prove the infidelity. Second example, a man with the same financial position as the first example divorces his very faithful wife because he has fallen head over heels for his new GF.
In both examples, assuming that the man and wife are exactly the same from a financial perspective, the outcome would be exactly the same. She gets half of everything that was earned during the marriage. If she didn't have any income during the marriage, she gets spousal support. And so on...
The other major thing to remember is that point about "getting half of everything earned in the marriage". Depending on what you do during the marriage, it might be in your best interest to divorce as soon as possible. This is from a financial perspective.
Good luck bro OP.