I just bought a 40z two weeks ago for $299 at a local car audio shop.
The Nak manual states that it does not play cd-r's but it also states that there are 2 pick up lasers. 1 laser for manufactured CD's and 1 for CD-R's.. sounds like double talk to me. In any event every Nak I tried so far has played every CD-R I have, and it has not skipped yet, even on dirt roads and speed bumps.
The only thing that I do not like is there is no dim option that I can tell. since I had laser eye correction bright ligths at night hurt, and the radio could be a tad bit better at getting far stations. Other than that my non amped system sounds good.
Hope this helps.
