Thanks for the replies - I always find a lot of intelligent views on this website.
I did listen to the 370 on its own - and it sounded great - especially for something 'free'. But then I went back to the 573 on its own and it made me realize again how much I liked it - and that there wasn't much I could criticize.
The whole thing also made me realize the joy of 'just listening' carefully to music again - rather than just mulit-tasking and doing other things at the same time.
And as space actually is an issue in a Manhattan apt it became a no-brainer to pass the 370 to a more needy friend.