s3 arms and console bushes won't affect your geometry. TT arms will, but s3 arms are the same dimensions as a regular gti/vrs I believe.
I had TT arms previously but now run s3 arms and bushes with superpro camber adjust ball joints. The arms give you a weight saving, the bushes are stiffer (non voided) and with adjustable camber ball joints you can run whatever geo you want. It's a very good setup.
I got my TT arms from a breaker, but the s3/cupra arms i have now were bought new - i got these from AKS, can't remember exactly but I think they were only about 110 each (arm + console and bush).