I sold the wife's Audi S5 privately a few weeks ago. Trade R291k. Retail R309k. I thought that was a bit optimistic, but that was the book. Anyway, went to WBC, vand they offered R180k. I was aiming forn R250k, as I thought that was quite realistic. But WBC's R180k was a slap in the face. I did not even rely to their offer.
I advertised it on Autotrader and Cars.co.za. Only got a few dealers that wanted it on consignment, so did not bother. I also advertised it on various Facbook pages, and that is where I sold it for R230k. Seems like more people are on social media that on the WWW. So my suggestion is to go that route.