Actually, I disagree with that Rmac.  In certain vehicles that are not
equipped with such features as satellite radio, GPS, etc, or only available
as a costly extra, you can purchase a very higher quality aftermarket head
unit with all of the features you desire.  For instance, in a vehicle that
does not have the option to add GPS, you can do this easily with an
aftermarket unit, as long as the new unit is the same size as the original,
or there is room to add a double DIN unit, such as some import vehicles.
Most of the newer units have multi-colored displays, which can be changed to
match the interior illumination lights.  As far as wiring the new radio in,
you can buy harnesses for almost any type of vehicle which saves you from
hacking the original harness.

Just my opinion
Sharky