Thanks very much for the suggestions, and for the helpful link.
It's always difficult trying to choose audio gear without hearing it!
I don't think I'd ever want more than two tracks. It's for "live" recording my guitar and a drum machine, and I'm mixing the two together before the recorder, so I really only need a stereo recorder. I've tried a Zoom H4n, but it seems relatively noisy, and sound quality isn't as good as my more expensive audio interface. I've since read that the H4n doesn't always handle level signals very well, especially +4dB line levels, which will require an attenuator. I'll need to experiment a bit more with the Zoom, but I'm really looking for something which sounds really nice while allowing me to record away from a computer.
I'm not really aware of current options, other than from web surfing. Would one of the mid-range recorders listed above (such as the PCM-D100 or Nagra SD) sound great, or do you have to look at something much more expensive, such as a Nagra Seven?