I think it's the best filter, but I don't have a lot of experience with other filters
In gph, it's unmatched by any other canister filter out there, though pond filters could compete.
I see you've got a couple of RES about 4". I think they should have no problem with the intake. There is a big intake strainer, so you can't feel much suction. The output is quite strong, but if your turts have problems fighting the currents, you can aim the outputs towards the wall of the aquarium.
In short, it doesn't even compare to the 405. I had the 404 in my 75 gallon, and just replaced it with an FX5. It's got a lot of really nice features that the 405 doesn't have, self-priming and the ability to drain your tank, being two of them.
It's a bit pricey, but well worth the investment. That's why I have 2 of them
Look around on ebay, and you should be able to find one for around $200+- with shipping.