The ATH-ADG1 are likely to have the same drivers as the ATH-AD700X (which everyone loves for gaming), so as for quality for gaming I don't think you can go past them. If you buy the ATH-ADG1 they come with a USB-DAC, which is likely better than your default soundcard and good enough for the headphones. As for the recommendation that you should get the AD700 (or AD700x) and get a clip on mic, this is what I did and got the recommended Zalman clipon and it was worse than a cheap desktop mic I had for years. It is a cumbersome solution, and with the quality expected out of the ADG1, I expect it to stop being suggested. I ended up getting a Blue Snowflake, which is an excellent mic if you are willing to pay.
One thing I will note is that you really shouldn't pay Australian prices for either of those headphones. The ADG1/AG1s come out on December 13th for the rest of the world, and you will probably be able to get them for significantly cheaper than the AU price, I would say closer to $200. If you can't wait, get them without the Xonar D1, should be able to get them delivered for under $300 through pccasegear.