66dB is perfectly reasonable if you are potentially dealing with things like ribbon mics, you don't need it often, but there are times.
Most of the complexity is in the stuff around the outside, protection against P48 accidents, RFI measures, the usual.
It is a bit of an old school job and you can get similar performance out of a single chip these days (But you still need all that stuff around the edges to make a reliable design), the major upside of some of the modern parts is the use of a servo to do the DC control, makes for a much more reasonable cap value.
Have a look at the THAT Corp datasheets and app notes for a single chip design that works really rather well.
Regards, Dan.