Good advice from batsbrew.
OP, do gird yourself for a barrage of comments saying to never mix with headphones
I went on Massdrop and got the Hifiman HE-4XX for $170. Great sounding planar-magnetic, open-back cans. I don't do a lot of polish-work these days, more of demos and gumming around in the studio on bass guitar and various synths, so for stuff like that, I have no issue using a pair of good cans rather than bothering everyone in my house with the monitors. Sound-wise, very balanced, just good, even bass, treble, and mids all the way through, of course EQ'able to taste.
The build quality is also
great in my opinion, very solid and on the heavy side, something that's very important to me when buying gear like this, not much skimping on material quality.
I also just love giant headphones!
Not
necessarily condoning them for mixing use, but I do like me some headphones/IEMs.