That will work, but it won't connect the reset button, case speaker, HDD LED, that sort of thing. The better way to do it is to use some tape, mark each wire with what pin it goes to, then just a small jewelers screwdriver or the end of a sharp knife to bend back the retaining clip on the metal sleeve inside the connector block and remove the wire and sleeve from the block. Plug the wire onto the pin it corresponds to.
As far as the microphone, look in your motherboard manual for the front audio connector, I forget what Asus calls it, something starting with an A. Ten pins with one pin on the end missing. Your manual will have a pinout of which pin does what, so you know where to conect it. Again, you may have to remove the connector block to fit the wires on the pins (if it's in the middle, the block won't fit between the rows of pins). On my board, an older Asus, the front panel header is located on the corner of the board, bottom rear if you're looking at it as mounted in the case, below the PCI slots and very close to the edge of the board by the expansion slot covers in the case. Should be green, I don't think Asus changed that.
Faster than the speed of snot
Two wrongs don't make it right, but I sleep pretty good at night