OK i have to buy a new CdPlayer so i found a 2004 Audi A4 SYMPHONY II will it fit in a 2000 A4???

 

Yes but you'll loose some functions. Check out audiworld's tech section for a write up on how to fix some of the problems.

 

for your 2000 A4, the closest fit in OEM headunit faceplate is a C5 A6. The B6 A4/S4 (2002+) is much narrower and will need much more fabrication to fit.

See my links below for related install pix, help, ideas etc.

Good luck!