I agree headphone mixes can be great.
Just a thought, I think anyone with the equipment they have can make a a) bad mix b) an ok mix c) a good mix and d) a excellent mix.
You do not have to have a sub I mean how did they mix without them and subs have been around for a long time.
Major studio's get by Mastering engineers have always gotten by and from what I hear abbey road studio's got by with what they had for those days.
Maybe times have changed but I still am of the persuasion that you can do much with little and little with much, it just depends on how you utilize it and how well your willing to learn and put into it.
I was listening to Floating by Yori Yackin and was amazed at how much bass was lacking from that recording. I was flummoxed to know that it was Cakes staff that had a large hand in it.
Then I read this, please have a listen at the release and see what you think!