The Symphony is already a double-DIN stereo, so there's a little confusion about what you're trying to achieve. Does your car currently have a single-DIN Concert unit and you're looking to change to a Symphony?
I opted for an alpine double din radio , there are various lead kits available but youd need to buy one to fit the type of radio your replacing your symphony with, There is no double din facia available for the A2 so youl need to buy one of these, and then file it down to size, i used a grinder to take most of the material off and then filed and sanded the last few mm til it fitted snugly..