I use a pair of Ascend Acoustic CBM-170 monitors and consider them to be un-discovered gems. They strike a great balance between being very accurate but not at all harsh. I can work with them for many hours straight without wearing out my ears and mixes that sound good on them transfer to other systems very very well.
Passive monitors, as with all small nearfields they drop off at about 100 hz but they dont try and fake it below that. From 100 hz up they have one of the smoothest response curves you’ll come across. I combine these with a 10" Yamaha sub and this works very well. The Yamaha sub is clean enough to get me pretty close on the low end, then I cross check against a main monitor system with an HSU VTF-2 sub.
The CBM 170’s are solidly built and very reasonably priced ($348 a pair). Studios and musicians dont hear of them because they market to the home theater crowd and sell via internet only. Prior to that I used several different models of Tannoy’s which I liked (again, because mixes transfered really well to other systems).