I've been researching the 13x6's lately. I hope this helps
Superlights-
23P will fit a MK1 with 205 tyres
13P will fit a MK2 with 205 tyres
13P will fit a MK1 with 185 tyres
JBW RS4's 30P will fit a MK1 with 205 tyres
16P will fit a MK2 with 205 tyres
16P will fit a MK1 with 185 tyres
I was keen on some RS4's with the 16P offset thinking they would have more dish than the 30P. But the dish is the same. All the manufacturer does is put more meat on the back of the rim :(