I agree about the 661. Go to Oade's website and buy a modded box direclty from him, or buy a stock one and send it out to Busman.
The 660 is a really good box, but if you're jumping in, I'd also suggest going straight to 24bit, mainly because you'll have a much harder time messing up recordings in 24bit-land than 16-bit because of the headroom you get with 24bit...you can run at -12db and never worry about peaking in 24bit and your recordings will never suffer for not running right up against the edge in 24bit.
Another option would be a small preamp like the Aerco MP-2 into an R-09HR or a similar small 24bit handheld. The problem with that suggestion though is the Aerco is impossible to get unless you order one, which then takes months to receive. If you know where to find an Aerco though, that would be a really great sounding option.