Welcome Kislik
The following are common replacement parts for CSLs here in the UK:
Brakes - AP or Alcon (K-Sport & Brembo less popular)
Suspension - KW or Intrax (Bilstein, Nitron, Moton less popular)
Exhaust - Supersprint or Milltek
Based on what you say it will be used for i would not bother with different suspension if you will only drive on road and the Ring. You might want to check the standard springs for cracking. I would also fit the RTAB to the CSL as it will definitely benefit from them.
Rob