I'm brand-new to MD recorders; but thanks to a local garage sale, I have three of them now in my possession: a Sony MZ-R50, a Sony MZ-R700, and an Aiwa AM-F70. I've decided to keep one, and sell the other two. However, I don't know how to decide. I'd like to a) record some acoustic music; and maybe also use my MD as an MP3-type player. I understand that the Sony MZ-R50 is considered to be among the best MD recorders ever made; but how is it better than the Sony MZ-R700, which was released a couple of years later? Is there a difference in sound quality re. playback and recording? I also undertand the R700 can be hacked to unlock some extra features. Thanks goof_chewy (not my real name)