Nobody,

If I installed a 530, the receiver and install would
probably cost close to 80% of the value of the aircraft.


If you did that, I don't think you'd need an external annunciator.
There are some GPS units that don't. Aviation Consumer has done several
stories on when an upgrade makes financial sense and what kind of
upgrade does. Their archive (for a fee/subscription) is online at
www.aviationconsumer.com

--
Thomas Borchert (EDDH)