Great; happy honeymoon!
I wasn't 'questioning' your decision; I was merely pointing out that it appears, at least to me, there are more cost-effective and more beneficial ways to travel SYD-SIN in business than purchasing economy seats and paying about $1,400 for one way upgrade. I am sure you have had your own, very good, reasons.
I am not sure if SQ has upgrade bids, but I think you can use SQ miles to apply for upgrades (again, not a great use of SQ miles, but it might be an option in your case).