I use a FocusRite VRM Box and BeyerDynamic DT880 Pro phones. After a lengthy break-in period on the phones (about 200 hours), they are very detailed, "even" and have plenty of low-end - much better than any set of nearfields without a sub. No problems with my mixes.
I think most people think low-end is lacking in phones as they can't "feel" the bass like they can with a subwoofer. I don't have this problem. I guess I don't need to "feel" it. Your experience may be different. The biggest problem with phones is that the stereo imaging is absolute. You get no cross-signal like you do with your ears naturally so properly panning your instruments can be a little difficult. The plugins listed above (I used Redline Monitor for a while) or the VRM Box compensate for this to make it seem like your mix is out in front of you instead of inside your head.
With any monitoring setup (speakers or headphones) you will need a little time to get use to how it sounds to produce decent mixes. I've been using headphones for years, so I am use to it. Adding the VRM Box has only made it better, although it took a little time to get use to the change in sound. It is nice that I can check my mixes in different simulated environments with the VRM Box. I was kind of skeptical at first, but I wouldn't give it up now for anything. It really works, and it works very well.
I do have a set of Focal CMS-50s, but I still mainly use the phones and just check my final mixes on the monitors as well as a set of Klipsch Pro Media 2.1 PC speakers. I haven't yet had to make adjustments after listening on the monitors or other speakers.
If you opt for a VRM Box, make sure your current interface has coaxial S/PDIF out to go into the VRM Box, or just use the VRM Box as your interface (I haven't tried it as a stand-alone interface). 250 ohms is about the most the VRM Box amp will power, so make sure your phones don't exceed this if you are considering the VRM Box as an option.
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My setup
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Echo Gina3G PCI interface: Analog out 1&2 to monitors, Analog out 3&4 to PC speakers (with adapter), S/PDIF out to VRM Box / Phones (see below)
In my DAW software (Studio One Pro) I set up a separate stereo cue in my Outputs and run that out through S/PDIF, that way I can have my phones and monitors running at the same time, though my monitor volume is usually turned down until the very end of mixing/mastering. Your audio interface may support simultaneous analog and digital output in its control panel (mine does not), so you wouldn't need to set up the cue mix in your DAW.
Hope this helps a little.