+1 to the reference track.
I mix mainly on a good pair of headphones through a VRM box. And no matter how good it sounds through the VRM simulations, there will be times when I listen through my crappy Bose computer speakers and it just seems so boomy in the bass and muddy in the low-mids. So then I listen to a mix that I know is excellent, maybe one of Donald Fagen's solo albums. And although it's obviously way better than my mix, I do notice a similar kind of boominess and muddiness. I have thereby learned something about the Bose's, and that I'm chasing rainbows trying to get my mix to sound perfect on them. I could seriously cut those lower mids to almost nothing, but then I'd just have a mix that sounded brittle on everything else.
So it's a compromise. You have to become intimately familiar with all of your speakers and headphones, and check the mix on as many systems as possible. This is where something like the VRM box comes into its own. If I mix something on headphones without the VRM box, I can get it sounding absolutely fantastic and then when I listen to it through the VRM box it's clear I have way too much low end and mud. So I adjust the frequencies until it sounds good through the VRM, and then I worry that it's going to sound thin through raw headphones again. It does at first, but after a while my ears get used to the new "balance," and it sounds just about right. Your ears take a while to adjust sometimes. Often you will feel so pleased with a mix as heard through one system that you don't believe it could sound good any other way. But there is a happy compromise in which the mix sounds good on all systems, and I guess that's the holy grail of mixing!