I tried a few... actually 5% difference was the best case scenario using Hang Seng's valuation. Bank of China has a valuation which is $170k less than Hand Seng's :O!
I don't know why my agent is telling me it's fine. If it falls through based on this they'll get to make their commission a second time, but it can't be fun for them or good for their reputation.
I guess I could sign a preagreement with a clause that finance is successfully approved for the accepted offer amount. But I doubt many sellers would go for that.