The idea to go with a class 10 card was perfect. I can copy the music very fast on my focus . I got this card for 33$ in India.
Thanks for review.
It's definitely working good and I've had no issues so far. However I didn't get to fill half of the ~40 gb yet so I can't make a firm 100% promise.
Again refreshing the thread: the complete list of working cards compiled from this thread up to now you can find in the Focus wiki.