It sports some fairly tacky Valentine's Day theming, but HowMuchDoYouHeartMe.com does perform a potentially useful function: letting you set the budget for a trip with your partner and then seeing what flight and accommodation options are available for weekend getaways.
The site is from the team that created the Adioso flexible travel search tool which we mentioned last October, and lets you choose a budget between $500 and $3000 and set any Australian airport for your departure. Once you've done that, it shows flight and hotel deals over a range of upcoming dates.
I couldn't find any bundles for $500 from Sydney, which suggests that the range of options being explored isn't wide (as well as confirming the non-news that I am fantastically cheap). I wouldn't make it your sole option when planning a romantic trip away, but it's a potential source of ideas.