In the under $1000 range, I would say the Tesoro Lobo Super Traq or the Fisher Gold Bug 2.
I don't own a Gold Bug 2, but it's a really good machine. It's made for gold and it operates at 60 Khz. Which means, the higher the freq. the smaller the gold you will find. To compare, the MXT operates at 14 Khz, not bad, but just about any metal detector will find what an MXT will find. Most professional nugget hunters use the Gold bug 2 if they arn't using a Minelab. Another good thing about the Gold Bug 2 is the coil selection, 6", 10", and 14".
A little less expensive than the Gold Bug 2 is the Tesoro Lobo Super Traq. I can speak from experience with this one. It a three position soil condition switch; normal, black sand, and alkalie. It has three modes; full range discrimination, all metal, pin point. It has an auto tracking ground balance in all metal mode, and fixed ground balance in discriminate.