As music is very subjective I worry about 3rd party selection. I think letting the artist decide their best tracks is probably the most sensible option. 5 is very generous. I think the 3 best would cover it.
I have no music on here precisely BECAUSE I want to make sure the stuff I put up is of quality. I mean look at the list of users. But maybe I'm overly critical.
One man's trash is another man's treasure. Just because you may be overly critical of a song doesn't mean there isn't an audience that would truly enjoy it. I admit I, myself, have questioned bringing out tracks on all mediums and receiving great reception a number of times even though there's moments where I feel the need to change things in a song.
As a musician, our songs are never quite finished, and we'll always find something new to do with them, much like an artist and his works. It's how we present them in the end that matters to the audience. I personally thank An0va for giving me that advice before when I was first getting into writing chip music.
That being said, this is a fantastic idea for the site. Even as a new member to the CM.org community, I have some deep roots now with the Philadelphia chip scene and personally, I feel this move to limit the amount of songs stored here is a great idea! Soundcloud integration is great but it limits what file types you can upload. Should someone want to upload nsf or a number of other native file types, they're SOL. Just my two cents.