There are essentially three types of players out there: FlashRAM, CD-R, and jukebox.
FlashRAM is like your Samsung Yepp. The largest in terms of storage I've seen is 128 internal plus 128 external. I have one of these, the MPIO DMG. Good chance there are larger ones out there now though.
CD-R is like a Rio Volt. Burn your MP3's to CD-R, pop them in, and off you go. The good part is that CD-R's are cheap, if you have a mp3 car deck they will work there, and it plays audio CD's. The bad part is the players can be kind of big (Volts are but the iRivers aren't), and 700 megs really isn't much when you have a large mp3 collection (I have 3000+ songs at over 20 gigs). These also don't tend to cost very much.
Jukebox is like the iPod. Transfer everything to a 5+ gig harddrive via USB or firewire. Pros are the large capacity for songs, form factor is pretty good too. Cons is basically the price. I have a Nomad 3 by Creative (20 gigs) and it kicks ass. The USB 1.1 is fine so long as you don't swap out more than an album or two at time. Loading it up the first time tacks a long time, but after that its easy.
So take your pick.