im looking to upgrade my brakes on my mk4 gti as the pads are on there way out... i was thinkin of upgrading to larger front and rear discs to vented ones... but what size am i looking at?

as i belive the front and rear will be different sizes even if i do get larger discs??? also will they fit fine if i have original golf mk4 gti 16" rims (check the pic)
http://img7.imageshack.us/img7/8/pic0001y.jpg