I've had my 850GLT with these wheels for the past 9 years and use 205/50ZR16 87W's. Used to use Pireeli tyres but have c hanged to Kuhmo as they are half the price , last twice as long and theres not much difference in handling.
i would really stay away from any tyre fitter that suggests the corret size tyre for wheel that already has 16" tyres on is a 15" one you can use 205/50/16 (standard on T5's) or 205/55/16 standard on the lesser performance models
--------------------- 00' 323ci almost 100k miles, looking towards a new ride...