I have an Eheim 2080 and it wouldn't be my first recommendation picking from Eheims. I have it on a 125 gallon and added a Fluval 406 to take care of mechanical filtration, because the 2080 wasn't cutting it. My 2213 and 2217 work great though.
It's really hard for me to suggest a big eheim. The smaller ones come with media, so the price is pretty reasonable. The 2262 is 3 times the price as the 2217. The 2217 includes all media and the 2262 doesn't. I'm not arguing the quality of an eheim. It's just hard to justify the 2262 or 2080.
I'm pretty sure Harley K measured the flow rate of a 2262 below 500 gph. It's generally agreed for a heavily stocked tank to have 10 times turnover of the tank volume. Based on that you should need at least 10 2262s for a 500 gallon tank.
People like to criticize the design of the fx5 and how it limits media volume. The extra media capacity of a 2262 or 2080 is useless. You'll only grow as much bacteria as your bioload requires. The flow rate on the filters needs to be more balanced with the amount of media it holds.
I'm not saying an fx5 is better, because based on measured flow rates of around 500 gph you'd need 8 to filter a 400 gallon aquarium. That is if you're using the filters only with no type of powerhead or supplemental circulation.
I really think the aquaclear 110 and a canister is a great suggestion.
All manufacturers overestimate the size of tank their filters can handle. The eheim 2080 or 2180 is only rated for 320 gallons, so it's not likely it would keep your tank clean by itself. Harley K is one of the biggest Eheim fanatics around and even he says do to the faulty design of the Eheim 2080 and 2180 that he wouldn't use it on a tank any larger than a 75 gallon.
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