if i bought a class 2 vs a class 6, would the x920bt be able to tell the difference ie read one faster than the other? is it a noticeable difference?

Songs, no. Video, maybe.

the class is referring to write speed, so a faster class would take less time to dump your files from your computer.

the class is referring to write speed, so a faster class would take less time to dump your files from your computer.

Technically, yes. However, read speed also increases as a byproduct of higher quality flash memory.

Technically, yes. However, read speed also increases as a byproduct of higher quality flash memory.

exactly