Wait, I thought there was more like a $4-500 difference between Streetlines and Silverlines and only a $300 difference between Streetlines and Highsports. IMO zinc plating and dampening adjustment is worth $300, but probably not $500. Also, no I really don't think theres a $300 difference between Streetlines and Highsports since the only difference is the plating.
Also 8.5J et32 isn't that crazy if your low with rolled fenders and a 205/40.
Double edit: Smallest 19" tire they still make is a 215/35, and I'd not recommend that from what I've heard about the roads in South Africa. I'm all for small tires, but cutting down that much sidewall is a bent wheel waiting to happen.