If you absolutely must have all of your media with you at all times, Wolverine's latest entry in its ESP 5000 series of media players might be what you need. The US$549 ESP Model 5160's 160 GB of storage space is enough for an estimate 50,000 songs, 320 hours of video. It also sports a reasonably sized 3.6'' LCD screen.
Much like the Wolverine MVP I wrote about last March, the ESP 5160 is crazy with data I/O and supported formats. Aside from the expected USB 2.0 connection, it can also get its media via its 7-in-1 card reader, and supports NTSC/PAL video out. Supported media formats are JPEG, BMP, TIFF and RAW for graphics; MPEG-1, MPEG-4, Windows Media Video 9 and XviD for video; and MP3, WMA, Ogg, WAV, AAC (MP4) and CD-Audio for audio. Best of all, that's native -- just copy the files over and you're done, no transcoding necessary.
However, it seems that, as with the MVP, Wolverine's description of its device is revealing. On the Web site they refer to it as a "Multimedia Storage Player" -- implying that its job is more about storage than playback. Melissa Perenson's PC World review of the 5000 series seems to bear this out. Still, right now the ESP 5160 has the capacity and price point to beat.