I have a 404 and really like it. The only thing I've found is that the inlet at the disconnect seems to be more prone to cloging than my rena's, but a nice filter none the less.
I might think about going for either the 305 or 405. Always better to over filter than under, and mbuna can be messy.
Fluval cans are probably the BEST i've ever come into contact with, I use a 304, bought it the week before I started seeing 305's in catalogues, DAMN!
Nontheless, a very nice canister filter, go for it!