I actually ordered the Lanzar VX420s to replace a place of 'factory' 4-inch loudspeakers in the dash of a 1986 Toyota Pickup (actually a Sunrader Motorhome). The physical build quality of the speakers is very good - cone materials appear very durable, nice rubber surround and an extremely hearty magnet. The installation materials were stable, including above-average speaker cable television with good terminations. The speakers fit nicely in our factory openings, though if the room behind your speakers is tight, you may want to double-check measurements as the magnetic structure on the VX420 is big (and heavy).
Once the herbst is installed, the sound is, well, amazing! The clearness and imaging is exceptional. Lanzar has been doing an incredible job packaging a lot of loudspeaker into such a very small package. Now keep in mind that a 4-inch driver is not heading to move a great deal of air on the low end of the spectrum, but when they hit, they hit hard and tight. Testing a variety of music styles, I found instruments showed very naturally and the lower end tight and clear.
The rear speakers in the truck (actually the 'coach' in the motorhome) give the 'deeper' bass, and I am so impressed with the VX420s, that I'm looking at other larger speakers from Ponerse to replace the manufacturer set. Can hardly wait around to hear what's next.