If you want speed you want something like the Claas Disco 9100 or other butterfly disc mowers.
Not at all cheap though... and you'd need a mid sized tractor to be able to power it.
Otherwise you could look at this sort of stuff, as examples (not that I recommend JD equipment over others).
http://www.deere.com/en_US/docs/html...id=729db26d#14
http://www.deere.com/en_US/docs/non_...otary_Cutr.pdf
http://www.deere.com/en_US/docs/html...?id=3a96d8a9#1