So my problem is that I what to buy monitors to produce mix and master, and I'm able to spend around, 900$, but I don't know if I should buy a pair for producing and another to mix, a pair that allow to do the 2 things(what a think it's a bit difficult because I want to work with some bass and that may get in the way when I'm mixing) or buy a pair with a sub.

What do you think I should do?
Can anyone help?
What would you do?