I have the S500s. While they do have a good sound for a headphone that is designed to be very portability, keep in mind that the people that are talking them up have also generally changed out the earpads. They are also not for sale in the US yet, which makes returning a faulty set or warranty work a problem.
people are changing out the earpads primarily to increased comfort and listen to them hours at a time, they still sound good with the stock pads
they are cheaper new than the above mentioned used vmoda
they run for around $50 without shipping while the vmoda run around $160 new
there hasnt been any complaint about a faulty pair so far for the jvc and if there is concern, they are cheap to replace
edit: but by all means, if vmodas are the style your son likes, go get him one