The whole point of changing them was weight saving!!
Anyway,
Cup Speedline (Road use) are 7.5x17
Cup Speedline (Competition, by Renault Alpine) are 8x17 but they're not ment to be for road as they are made of magnesium and therefore they're welling to bend easily!!
It seems that I might go for OZ Ultraleggera Matt Black 8x17 as they're 7,74 kg only!!
Or even 8x18 8 kg only!! But in this case I might need to lower it or would't I?
If normal cup speedlines are 9 kg and competition cup rims are 10.5 kg as "alt197" stated since he just got them then why would I get them over my OEM 7.5x17 10 kg rims!! And they're available at our local stores so no waiting is needed!!
Have a look at this link where they got all sizes and weights: