Rich, I don't have that big a yard but I have a BIG cottonwood tree and a couple of maples. The maple leaves are not bad, the cottonwood leaves are murder. Since they tend to stay flat after falling, they are tough to rake. I have never seen a mower that would do much to them. My suggestion would be to look at a leaf blower and a chipper/shreder. If you have that many trees, you will have branches come down, or you will want to trim them eventually. Going that way, you can make everything mulchable or bag them more easily and densely for carrying away.
This turned out to be an interesting topic, with as many answers as there are lawns. Personally, I have never spent over $125 for a mower and they last 5-10 years. Hope we haven't confused you too much. Henry in MI