You need a hay mower - as Anke has said, a topper minces the grass, which is not hay. It's worth getting the right equipment for 6 acres. A mower has two rotating discs parallel to the ground, and a skirt like a hovercraft to catch whizzing stones. It leaves the grass lying in swathes as if it has been scythed.
You will also need a hay bob to turn and row up the crop. It's the thing with two rotating cages with tines.
Then there's the baler. We got ours for £500 about 25 years ago from a scrap dealer who got it going for us initially but now my husband maintains it. (the other machinery we got very 2nd hand in machinery sales). Our little Siromer can manage most of the machinery but is not big enough to run the square baler - we use our very ancient David Brown for that