Since SparkCore uses a 72MHz uC and a 54Mbps wifi shield,
this can be done?
Is it possible to get a stream from the internet from the sparkCore?
Spark compatible audio shield? Or any should do the job?
Limiters?
We haven’t tested high bandwidth applications with the Spark Core so we’re eager to see someone take a stab at it!
Streaming audio might be difficult because you need to buffer the incoming stream, and the memory on the Spark Core is very limited. Worth trying though 
Best bet would be to find an Arduino shield that fits your purpose and use the Shield Shield.
Took a longer look at the post and realized that it’s an Arduino they’ve got set up; if an Arduino can handle it, the Core definitely can