My Sonus Faber Amatis have weak bass even though I'm running ML 536s--800 w/ch into 4 ohms

I have a similar sized room. If you have ruled out wiring problems you may want to return the speakers. It wouldn't be the first time something Italian left the factory with a problem. 

I am running Yamaha NS-5000's driven by Wyred 4 Sound SX-1000R monoblocks with a Rythmik G25HP subwoofer. Bass is fine on axis. 

You may want a full surround system from what you write. Get three bids from sound installers. Big rooms are trickier. 

well why is this unexpected, bass response is directly proportional to a speakers output, vs room volume, and his space is gigantic, when you combine all three rooms contiguous volumes, so of course you need subs.

Dave and Troy

Audio Intellect NJ

@Audiotroy--never thought the room was that big, but you may be entirely right. I assumed it might have something to do with the fact that there is a half-wall between the living room and the kitchen. Maybe I just need the subs based on the size of the room.

@jl35--that may be it too. I really didn't expect to need subs. Or at least I was hoping that if I spent that much money I wouldn't need them. 

I guess as a side note--I usually buy used equipment because it let's me get things at a fraction of the cost that I would never be able to afford otherwise. The SFs and the MLs were both used demos from authorized dealers. With the SFs, the dealer was from out of state, so I didn't get the benefit of having someone come in and set them up. It has occurred to me that something is broken/wrong/malfunctioning, but given that the bass I am getting sounds good, my guess is that everything is working properly. It's not like the bass drivers aren't moving or producing sound. I just think there ought to be more of it.

Stupid question - is your judgement of bass based on critical listening with the chair in the middle or is bass lacking in general. It’s possible you’re sitting in a bass null.
Or the setup is just not optimal. Can you post pics in the virtual system section of your profile?