Quality is readily achieved with a carputer if you have the cash. Digital output soundcard with a digital input amp with quality drivers to suit. A standard sound setup using 3.5mm headphone jacks like most people here is all thats needed to be at the same DB level as the HUs, your amps will do the rest. DB is pretty different to quality though, if you want to beat the HU quality you will have to spend the cash and go digital. Non digital carputer setups have won DB comps.