I personally would (and probably am
) go with the Pio if 2.0 is meaningless to you. The pio will more than likely have better build quality, and a better analog section.
Pio is great with their FW updates also, so I wouldn't fret too badly about the update. I don't know for sure, but I would hope the player would get the update before the s550 is even released.
Pio has a 2 year warranty too.