Right now there really is not a 20GB player that would be comsidered the "best" by everyone here. You will probably get as many answers as there are people that come to this topic, it is really just about the features that you would want/need in a player.
IMO probably one of the most important question when picking a player is how you would want to navigate through all of you music. Do you prefer File-tree browsing (e.g. like looking in windows explorer) or do you prefer tagged browsing (e.g. as you would search for music through iTunes)
Second, what sort of extra features do you need. Like do you need recording abilities, an FM radio, a color screen.
Also do you requre a very small player. I have played around with several players and they come in all shapes a sizes. Such as the Zen players (Xtra and Touch) are relitivly large players, wheras compared to the Ipod or some of Sony's player are very much smaller.
And finally sound quility. You will find this is much of a mixed bag. None of the player are what would be considered "audiophile" quility. Most people will tell you that the Rio Karma sounds the best. I personally have never listened to the Karma, but I have heard Iriver's H-120 (the H-320 will sound almost identical), the Zen touch ( the Zen Xtra should be similar), and a 4G Ipod. I have had my H-120 for about 6 months now and I think it sounds awesome. I has a relitivly neutral presentation that I prefer. I was not ver impressed with either the Ipod or the Zen Touch. The Ipod sounded good, but the bass was a little to recessed for my taste, and the Zen Touch seemed to really strain to power my HD-280's which made it sound very tinney.
There really are just so many players out there now that it is really hard to recommend one to you without knowing what you would like to have in a player.
