As i read through the post, i am getting all these symptoms too right now..
1) Hear the nice high-pitch, high-class airplane "duuung" sound when i try to start the car

2) All car meter went berserk.. "ANTI-CLOCKWISE" and engine dies off as soon as the car starts. [yesterday morning]
3) Driver & passenger airbag light went ON [but this is intermittent, cuz the second time i start my car after resting 6 hrs, the light went off again]
Have not change the battery yet... will update again on how it goes!
Now need to survey which is best alternate battery.. cuz was told the ori cost RM5xx haha...
p/s: Item 2&3 when you first see it sends chill down your spine and gives you cold sweat

LOL i like Item 1) which you mention high-class airplane "duung". I can tell you is the battery is weak by using a device to check battery level may give you precise answer.
To me, i never opt for a fancy battery (depending on own preference) as i am out of budget to have 1. I am just using a local brand Century DIN55 which cost around 220. The guy came to my place and change for me and test to ensure the batt is charging before he leaves.
Sad to say i am too noob to change the batt my own + no tools. I always go for the options which best for me and hassle free.