Although I'm a newb myself, I dunno if I would go with anything that doesnt have vga input or at least a relatively high resolution. A couple of my friends have 6" and 7" lcd screens in their cars that they got for around $100 off etronics.com and they work great for watching dvds and playing console games on, but I borrowed one and hooked it up to both my via m1000 (which I'm planning to make a carputer with) and my laptop. On one of them the tv out on both boards wouldn't work at all and on the other the resolution looked like ***. I found a 7" lcd with vga and rca input that runs a resolution of 1024x768 (which I think is damn good for a little 7" lcd) for only $228 with about $30 shipping. Here it is
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2434442327 . That's the one that I plan on buying for my carputer since I also want to use gps, have a rearview cam, and watch dvd's and divx movies.
If all you're worried about is winamp then I guess a small res isnt much of a problem, but the smaller lcd I tried mine on didnt work at at all so who knows. Hope this helps.