Originally Posted by Wooferine View Post
So of course one weak link in the strongest chain will cause it to fail, but we can't all become end-to-end audiophile electrical and electronic experts just so our cars don't sound crap.
That's the answer to your question. There is no single most important thing that contributes to sound quality. You need a balance of decent hardware (speakers and electronics), decent installation technique and speaker locations, and decent tuning. The A/D/A conversions may have been important sometime in the past, but modern equipment is so good it doesn't matter so you can safely ignore that entire line of thought.

You don't have to become an expert in all aspects of everything. There are some really simple rules of thumb you can follow for each of those topics above. This is where this forum comes into play. When you want to tackle each part, just start searching and asking questions.

If I had to recommend something to put the most emphasis on first, it would be defining your goals. Do you want a one-seat audio experience, or do you want to entertain all of your passengers too? How flexible are you with speaker placement, vs how much of a perfect factory appearance do you want? What is your budget for everything? Do you have a certain experience you are trying to recreate (such as a certain car you have listened to), or are you just trying to get the best experience that (we) know how to build? And finally, how much of this are you willing to do yourself (and how much time do you have to invest), vs how much are you willing to pay someone else do?

If you really answer questions like that, then we can better guide you.