I've owned a Samsung YP-T5H. Good sound quality despite being only S/N ratio of >80db. 128mb not quite enough though, just 2 hours mp3 or 4 hours wma. WMA was fine on this unit. Really small as well. First impressions to other people assumed it was a battery.

Not sure of the YP-55H, looks good. Maybe the buttons are too small?

Creative Muvo TX FM. Muvo series are really good quality mp3 players. Good sound quality plus battery changing easier than YP-T5H - which sometimes feels like battery door will break off).

Recommend at least 256mb, preferably 512mb. Radio's are good as well, since you're limited to just 30, 60 or 120 mp3 tracks on 128, 256 and 512mb respectively. Longer headphone cord serves as better antenna for the radio...Jog dials are really nice to use. If possible before you buy, feel how the button press.