I could support your strategy if I knew that you had more cash to buy another machine in the future. ie: You're down-sizing from 2 to 1 game for quality over quantity, but expect to buy a 2nd machine down the road when money permits. Otherwise, I personally would probably prefer having 2 different pins over just 1 pin (my current position due to space issues).
My concern is that you've only owned your current pins for 1 month. Seems to be as though you might be more caught up in the "getting" than the "owning" and that can be dangerous. Even the mighty MM will likely not hold your attention for too long if you're moving through Tron and LoTR that quickly.
Can you honestly say that you've played your current pins to death? It's not mandatory, but one of the first problems I've found with this hobby is trying to "catch the dragon" -curb the insatiable desire to buy every cool pin on the planet. As soon as you realize that it's ok to enjoy the pins you have, and not to worry about the ones you don't have, this hobby becomes much, much cheaper.
Of course, if you do buy an MM, please keep me in mind when you decide to sell it. It's an awesome game.