You don't have to use canister filters. In my opinion canister filters are superior to Hang on Back (HOB); They do a better filtering job (no bypass) and are easier to clean). However, if you clean your HOB filters on a regular basis (once a month), you should be ok.
Remember, don't go by the manufacturers tank size of the filters; go by Gallons per Hour (GPH). I would get either a cheap canister with at least 300 GPH or get an Aquaclear 110 (500 GPH).
I have a 200 gallon with 2 canister filters (very clean); also have a 110 with 2 HOB filters, very clean. The filters have positives and negatives to them.
Good luck !!!
BTW, i think the Fluval *05 series are very expensive. A 405 (about 350 gph) is about $250 retail. Whereas, you can get a Fluval FX5 at around 900 MAX gph for $300.
A cheaper canister is the Marineland Magnum 350 (between $100 and $150). Not the most user friendly, but it's managable. It filters 350 GPH, and has a carbon basket, that I would load with bioballs for more bio-filtration. Also, the Magnum can also come with a bio-wheel attachment, for even more bio-filtration. Again, not the best filter, but it's a cheaper alternative.