These days, most electronics are almost disposable...they can be made cheaply with 21st century technology...but it still takes 18th century "hands-on" diagnostics to fix properly.
I have no problem buying home equipment through the mail...but I don't have a 3.2 liter engine in my media room either!
Car media has to deal with a more dynamic environment, and can be subject to more electrical interactions, such as improper installation...a good rapport with a local installer can ease that pain.
I too have had great success with dealing with local installers. Sometimes they troubleshoot (and fix for free) problems that ultimately stemmed from some other vehicle conversion that "stepped on" their install.
As complicated as home media can be, it's still just pluggin in the AC plug, and matching up the coax and RCA cables.
Cars are way too complex and expensive these days...trust the install to a local shop.
Consider how far your warranty will stick when you call the mail-order comany about a problem with a unit...they can always blame your (alledgedly) slipshod install.
