Streaming from iPad - How to get the best quality

[DaveFin]

I've recently invested in an iPad and my ambition is to stream music from Spotify to my receiver in the best way possible. 

As an official app for iPad hasn't been released yet, I'm using Spotable currently. I also have a Boxee Box which is connected to the receiver by an optical cable. By Spotable, the Boxee Box and Airplay I am off course able to stream the music already today.

Still I've heard people mentioning that it would be better to use Airport Express for several reasons (convenient, quality) without really specifying the reasons. 

So would it be a better choice to invest in a Airport Express and use it instead of the Boxee  Box? Would it deliver better audio?

All help and thoughts very appreciated!