I use Fostex PM05's. Very good, but I hear the Yamaha MSP3's or 5's are a little better (according to UK's Future Music magazine).
On either set, bass is lacking, but I seem to be able to compensate with headphones.
With the Fostex, I can do a full mix that 80% of the time holds up on any system. Sometimes I'll have to go back and remix a bit, but I'm always in the ballpark.
Fostex made speaker drivers WAY before they made recorders...