I'll back up the call for an ac110. That is a quality filter, worth every penny. As far as OTB go I don't think I'll ever buy another brand again after using that.
I would get rid of both plecos. Getting rid of just the plecos will help reduce nitrates and waste A LOT.
I agree with the other people about getting rid of the whispers and getting an AC 110. You should definitely buy an FX5 though. FX5 and AC 110 + weekly water changes would make that tank look clean. Or if you want your tank to be extra quiet, get an xp3 instead of an AC 110.