Hi Andy,
In the GTS in 19", you'd be wanting to go for the 9.5" front +17 & 10.5" rear +17, this is the most "aggressive" looking and will give you the biggest lip (94mm front, 107mm rear).
We are an official UK distributor for Rays/Volk Racing so if you need any help please don't hesitate to get in touch.
Best Regards,
Gaz