I'll give you the MP3's, but I won't give you the web browsing.  The DS may not have web browsing capabilities (yet), but if you've actually used a PSP to browse the net, you know that no support is better than the HORRIBLE support the PSP has.  You have absolutely no idea how painful it is to type a web address in on that thing, or even how long it takes for pages to load.  Trust me....  the web browsing on PSP is not a good feature.  It's more like a festering wound.
ill second that....the web browsing was a fun gimmick for the 1st page or 2 you view.....after that it is just plain terrible....
...and i tried to load ebay on it and it couldnt load the whole page bc it said the psp memory was full.....
ill stick to my PC for the web.....that is until i get my MacBook Pro this summer....