Best canister and CO2 diffuser?

I am currently in the market for a canister filter for my planted tank. i
am looking for the best but cost worthy canister out there. I plan to spend
atleast $150 on one and would like some expert advice on which one to get.
I have been looking at the Fluval 404 but i havent seen or heard any reviews
on it. Does anyone know about this filter.

I am also looking for a good diffuser for my tank (55 gallon). I would like
to get one that doesnt waste any co2. I have tried building my own but they
just don't seem affective. I am currently diffusing with a powerhead but my
tank seems to empty alot quicker then it did with other methods. if you
know of any diffusers please let me know what the name is or where i can get
some info on it.

Thanks for all your help.