you seem to be going after a Marantz PMD-670. let me tell you me thoughts about it. it's real limitation is that it doesn't record at 24 bit. I have also heard that the internal front-end is not the best quality, so if you run mic in, it'll be a fairly noisey recording. However, if you pick up a ua5 (or any other A/D converter, for that matter), you'll be sending a digital signal into the deck, and the internal analog front-end gets bypassed anyway.)
a lot of people here are going to tell you a get a Nomad Jukebox 3 (aka JB3). this is an .mp3 player, about the size of a discman. but it has an digital input, and records in .wav file (also limited to 16 bit). So if you've got an external A/D converter (like the UA-5), then a recording on the PMD-670 will be EXACTLY the same as a recording on the JB3. the only thing that the recorder is doing is writing the data for the .wav file.
now, let's compare the two units... a PMD-670 is designed for our purposes, so I'm sure it is a more rugged piece of equipment. and FLASH media is more reliable than harddrives, because it has no moving parts. However, at this point in time, a 2-gig CF card is about as big as you can get. 3 hours at 16/48 (or 16/44.1). get yourself a couple of cards, and you'll be all set.
the JB3, while not as rugged, records to .wav file on an internal hard drive. your options are 20-gigs or 40-gigs. 20-gigs should be plenty, and provides for hours and hours of recording (although I believe there is a three hour files size limit anyway, but at least you don't have to worry about switching media, just starting a new file).
both allow very easy transfer to a computer, for tracking, editing, and burning to CD. the big thing that the JB3 has going for it is price. you can pick up one from eBay for about $150...
so there you have it. maybe soon, marantz will release the PMD-671 (if the thing even exists?) that can record at 24/96. that's a whole different story. but in the meantime, if you're just looking to record at 16-bit, than either of these would be good. if you get the cheaper JB3, perhaps you could put the extra $$$ into better mics, or maybe get more than the digi-mod UA-5 with one of Doug's mods to the ua-5 front-end. or maybe look into a used Apogee MiniMe or Lunatec V3... just throwing out some ideas...