Just to restate what I sent to Adam.

I suggested going with the DPE R-16 since he is looking for an 18" wheel similar in style to the C20. A black or gunmetal center with a polished lip would look great on a slate grey 996. Custom color-matched centers are also available for an additional charge if you are seeking a perfect match.

Any grey car with wheels that are grey or black with a polished lip will ALWAYS look good and won't attract TOO much attention.

 

Polished lip and color matched slate face

 

Going with a wheel that has a step lip such as the BBS LMs or HRE 540 Series would eliminate that problem. But so would the 1 Piece Champions and HRE Monobloks...

 

so the HRE monoblocks do not have the water retention issue (ie, P40's)?

 

Black on slate looks fantastic.

Here are Work Brombachers (3 piece):



And the ones in my avatar are Volk TE-37 Time-Attacks (1 piece)