I'm looking to upgrade the powerheads in my 120 breeder, and am looking your opinions on what will be my best bet. I'm looking at either doing a couple MP40's or a Tunze 6215, I've seen both in action, and think they will both serve my tank size well. I do plan to upgrade to at least a 180 in the next few years and would like to buy something that will work good in that too. Let me know what you think.