About to buy some powerheads, and I would like some advice for a 55g.

[Enigma]

Being that budget is a concern, I would recommend that you go with the Tunzes for now. Yes, the MP10s are nice (I have two of them in my 40B), but you don't need them. You can always upgrade down the road. You can count on spending $50 to $100 a gallon in setting up your tank.

At some point in time you may very well have another tank---quarantine, hospital, frag, etc---where the Tunzes would be useful if you replaced one (or both) with an MP10 down the road.