Quality of music depends on very large number of variables .. and as Madhouse often points out that your system is as best as the weakest link in your system.
From one end, the source music (DVD, Radio, USB) is the foremost thing... then comes the importance of a quality headunit. The HeadUnit is connected to amps through wires .. Quality wires (RCA leads) are very important in communicating the signals without loss. Then come the amp(s) ... they need the full current flow to perform optimally. We often ignore the ground cable ... as advised by tech gurus, it should be thicker and better in quality than even the power wire... Then the amps feed the speakers ... the speaker wires should be excellent quality. The final product is delivered by the speakers.... they should be properly mounted.
The wiring should be properly shielded. Do not run speaker and RCA leads alongside the power cable. The magnetic field around the power cables does effect the signals flowing in RCA and speaker wires.
Sound deadening does not appear in the above text, but to my mind, its importance is like preparing the foundations of a building ... if you dont have good foundations, then the building constructed upon it will be weak and vulnerable ... Perhaps, the first step in any audio system should be sound deadening ...
Little things in building an audio system can make the difference between a pathetic/ mediocre system and an excellent system ..
I will just cite one example ... a subwoofer is nothing but a strong magnet with a coil around it ... flow in the coil, triggers the magnetic field and resultantly a paper/ plastic/ kevlar cone moves back and forth. If you hear a subwoofer without its enclosure, the result will be something that you surely wouldn't like.
For proper sound production, the subwoofer requires an enclosure of proper thickness MDF/ fiberglass. Its volume has to be calculated according to the particular specs of that model. Then a basic decision has to be made about the enclosure ... if you are going the SPL route, then you need a ported Bass Reflex enclosure ... and if you are interested in SQ, then a sealed/ acoustic suspension box is necessary.
After you get the box, then you have to do the sound deadening. Madhouse recommends fiberglassing the interior of an MDF box to ensure proper seal and to avoid flex. Then comes the sound deadening of the interior of the enclosure .. you can use products like Dynamat Xtreme and then a sheet of Dynaxorb ... following which, you need to fill the 50% volume of the enclosure with polyester (incase of a sealed box) ...
Finally you have to ensure proper seal of the enclosure and the subwoofer ...
I will cite another example .. when you purchase an amp, take the time to read its specs on the net. If you dont understand the terms, then do get help of a friend who knows the tech stuff ...
Car's alternator is usually designed to cover 30% load over and above the stock electrical system's needs ... for a normal audio system, there is enough power ... but if you stretch the limits, then you need to take several steps ...
It is imperative to have a circuit breaker close to the battery
A capacitor (one Farad required for every 1000 watt of the system) installed close to the amp, can provide emergency and quick juice to the amps when low frequencies hit)
You need inline fuses of proper amperage ....
The power cables need to be connected through distribution blocks ... ensure that the distribution boxes have fuses as well
Good quality battery terminals are imperative. They cost a lot but they are a worthwhile investment. Similar is the case with connectors ... preferably all connectors should be gold plated for minimum resistance in flow of current
Heat kills machines like amps ... remember to provide good ventialtion and air circulation. The amps installed in the trunk do not get much ventilation ... if you invest in a fan to take the heat away from the amps, that will ensure a long life ..
Having a good battery is necessary. There are batteries designed for large audio system ... brands like Stinger and Kinetik make special batteries .... the audio focused batteries are different from normal car batteries. Ordinary batteries are meant to provide maximum power during a period of 5-10 seconds for starting a vehicle. This is called Cold Cranking Power. However, for audio systems, the focus is not on Cold Cranking power ,,, it is on continuous supply of power at good rating to the system for parking lot listening to music. I would prefer to have an Optima Hybrid Yellow Top, which provides the best of both worlds .. i.e. cold cranking power and continuous and constant flow of power during parking lot music listening. They take a long time in discharging ... they have enough juice left after 1000 days of inactivity while a normal battery loses its power in a week's time
When you have a heavy system in your car (beyond 1000 watts RMS), you must seriously consider investing in a good alternator for your car. SUV alternators can bear a heavy load while car alternators are weak. Companies like Stinger make custom made alternators for your car depending upon the model of the car and the power load requirements. They even make brackets for holding multiple alternators for cars with heavy SPL focused systems.
I hope this post will help in assessment of your needs for a good audio system ... this is just from a basic learner's knowledge ... Gurus can surely add/ differ with what I have said ...