I need an entirely new car stereo, I was told that if i want an after market head unit that I need a CUSTOM BUILT housing for it to fit. Any thoughts?

 

That's bull****. The housing/bracket in the X300 will take most standard head units. They just might look a little funny because the face panel wont be the same shape as the stock one. But you can buy facia adaptor panels like this to make it look better: http://www.dynamicsounds.co.uk/autol...l-p-14776.html

The only 'customizing' I had to do to fit my Pioneer head init, was drill a hole on either side of the metal bracket for screws.

 

If you just put in a new head unit it will be recessed back into the slope aways. i thought this looked kind of funny so i took the old face plate off and cut away at the inside of it to fit around my new deck so it could keep the slope look. its really up to you if you want to custom make something or if recessed look doesnt bother you.