Ran the 184's into the mp-2 the other night without attenuators (they haven't arrived yet). In a smallish club, FOB, I had to keep the gain set all the way down to its min. setting (which for the mp-2 is 16db)... that gave me perfect levels actually, but I might find myself in louder situations, so I'm glad I opted to get a set of attenuators, which should be arriving any day now.
on the MP-2, if you use the XLR outputs, you are correct that the min gain is 16 dB. If you use the 1/8" output, the gain range is 10dB less, so the minimum gain is only 6dB. if you get yourself a nice cable to use the 1/8" output, than you can probably avoid attenuators altogether.
check it out, on page 2:
http://www.taperssection.com/reference/pdf/Manual_SoundDevicesMP-2.pdf