External Modchips
 

I seen USN modchips, I was wondering can anyone recommend me one??

The SBOX has been mentioend a few time on the forum, although I think it can supports CD-R backups, but costs something like $13. You still need an AR2 though I think.

Other than that, not to sure as I am a proud owner of a Messiah/Clone and would recommend it to everybody.

the USB mod is shit.
you still have to open the ps2, you still have to solder, and it will not play dvd-r or import originals.

I would advise you to get a internal mod. The usb mod will play cdr backups but not dvd-r backups. Depending on what version your ps2 is a origa chip would be a good choice.