Wheel & tyre options: OEM or aftermarket copies?

my 18" rs6 reps are lighter than the oem ones - ive had lots of cheap wheels and apart from being soft and easily bent, they are usually cheap, round, similar weight and easy to balance so no particular worries

if you can reduce unsprung weight by a significant chunk then there may be a handling advantage, but 19's with less side wall is going to spoil the ride and handling compared to 18s anyway. if you reduce the unsprung weight a lot then the suspension would be set for a heavier wheel and would be effectively stiffer than intended, so adjustable dampers would be the way to go.

if its looks that are a priority, then a good set of 19 reps that dont weigh much more than the oem 24-27lb sort of weight sounds like it should work well, but you could do with going to 235/35/19 or even 245/35/19 to increase the sidewall height as long as you can get a set with a high enough offset assuming they are 8x19

245/35/19 however are +2.8% radius (3% is generally thought to be the max error) and the tyres are expensive, but the sidewall is only slightly smaller than the 225/40/18 fitting. it should fit on an et50 8x19 but its highly likely to rub the arches (particularly the rear) at et45. 235 tyres will fit on et45 offset wheels (18 or 19) without catching the arches but you lose quite a bit of sidewall.

unfortunately almost all reps are et45 in 18" or 19" but there are some great quality very light rims at 18" or 19" et50 in castflow and forged but most of them make the bbs rims seem cheap....
have a look at http://www.golfmk5.com/forums/showthread.php?p=1746774