I just bought D3. I want to know who sell double din kit for subaru legacy 2006. they sell on ebay but for single Din only.

there is no kit. you use the stock radio brackets and some abs plastic, or a trim ring

This should do the trick. If you go to LegacyGT.com you will find several posts:

http://www.japanparts.com/db/partslist.php?dealer=&car=&middlesmall=&maker=&volkey=107-203-002