I sold my Sierra Cosworth 20 years ago, assuming the same condition today it would be worth 6 times as much now. Bought a late 944 turbo 15 years ago, it's worth around 4 times as much now. I don't regret the change, I was bored with the Cosworth, and I still like driving the 944. So mostly I agree with buying what you want. Though I think anyone that pays top dollar today, for an old RS Ford or Ducati R has more money than they know what to do with.