Replacing A8 carhandy

I have a 97 A8 and it came with the crappy carhandy GSM kit. I wanna replace it with Sonyericsson bluetooth kit. I don't know if it will be
compatable with the original system, I don't want extra mic or speaker since they are already installed and thinking of replacing the in-car handset as well. It has the Delta Bose stereo. Can anyone help?
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