I have a brand new Fluval 304 that I was going to use on my new tank, but I decided to get the Rena Xp3 instead and I am contemplating selling the Fluval for maybe $65 plus actual ship.
Otherwise the Rena XP2 should work for that size tank, new they are around $79 plus ship. I have heard of people going on the Petsmart website and printing off the Rena Xp2 that they sell online for between $78 and $84 and bringing it into the store and getting them to match the price.
At petsmart, they sell them for well over $100, but I know people who have gotten them to match.
Now they only match "THEIR" web ads, not big als or anyone else, but to save shipping and not to have to pay retail it is worth a shot and you can have it right away.
The Xp1 would probably have enough flow for a 55 gallon, and is cheaper, like $45 or $50, but it only has one media basket and doesn''t hold alot, but if your are using it more for mechanical filtration and using your plants and substrate for the biological then you would be ok
The Rena comes with the intake and out flow which can just be regular or the spraybar that is included.