Not a bad mix at all, I wish I could do that. If I may add some constructive criticism I'd say the drums and backing vocals are a little dry and the cymbals a bit tizzy, otherwise awesome work. Did you study audio engineering or pick it up through practice?
As for monitors it's good to use a variety though, my last mix was done using monitors and it sounded ok, I tried it through headphones and some of it was good but other parts were way too loud and out of balance. I guess thats why most studios have 2 or more sets of different monitors, and of course the old 80s horror story of using car strero speakers for monitoring cos thats where most people listen to music!