It hasn't been mentioned, but the 660 is 16 bit and all of the suggestions made so far are 24bit. You definitely want to go with a 24bit machine. The prices are reasonable and 24 bit gives you far more latitude in the live setting for getting the recording right since you don't need to run hot. In other words, the accepted practice of running levels has also changed from when you were last into taping...you don't want to set 24bit up near 0db because you'll lose all your headroom for when the show goes louder and you're not watching. Instead, run the levels between -12db and -6db and fagetabotit. You then adjust upwards in post without losing an bit of fidelity.
Don't buy the FR2LE. It's a good box, but no digital in. Don't buy the R4 unless it's a warm mod...it sounds like crap IMHO, unless you like tinny shrill sounding recordings. Digital input is resampled on the R4...which is a ridiculous design feature IMHO given the unipressive sound the box has in the first place.
The R44 is a great box, but it's a little bit dull sounding unmodded to my ears...modded R44s sound outstanding...great presence and great overall sound.
Personally, I think one of the best sounding boxes is the modded PMD-671, and there's a couple of those sitting in the yard sale right now for discounted prices because for wathever reason, the 671 seems to be out of style lately...which is ridiculous given how this machine sounds.
Personally, I enjoy having the flexibility of changing my sound up, so I have an outboard preamp and save size on the back end by using a hand-held R-09HR, which also does high quality A/D. It's not an all-in-one, but I sacrifice nothing in either sound or size with what I run.
Bottom line for me is if I was in the market for an all-in-one, it would be either a modded 661, modded 671, or modded R-44, with the R-44 probably being my first choice.