I have a 404 and 304 on my 75. I have a reactor plumbed inline with the 404 and can't imagine it providing enough flow on its own, especially with the reactor. As your biomass increases you'll need more flow, IMO. If you don't want to run the old filter in addition, I'd go with a Koralia powerhead.
I've had fluvals for over 20 years with no problems. I've found them quiet and reliable and never had a reason to change.
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