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

@torke

More watts aren’t always the answer.  I have the SF Amati G5’s and have PS Audio BHK 300 amplifiers that put out about 600 watts @ 4 ohms and I get amazing bass.with them being 91db efficient I rarely turn the volume past 30 and if I go to 40+ the whole house starts vibrating.
The speakers are 4’ from the front of the speaker to the front wall and 3’ from the side walls. They are 7’6” apart and my listening position is 7’6” from them.Oh ant they are toed in so they aim at my shoulders.

Having said all that, I can honestly say that it’s not the speakers. I have no knowledge of your amps or your room, but your room and placement make a huge difference in the sound of these speakers. What’s your room size? What is your floor made of? Do you have carpet? When you clap your hands near your listening position can you hear any echo? Same question but near your speakers? How far apart are your speakers? How far are you from your speakers? Before you got the SF speakers, what did you have? Did they seem lite in the bass also? Have you double checked that the speaker cables are connected correctly?
 

All the best.

@torke 

I was just reading about your amps and I have another question or six.  What are they plugged into? Are they sharing the same circuit? Is it a 15 or a 20 amp circuit? Are you using a power conditioner? Are you using the stock power cords?

All the best.

May I respectfully suggest our Caldera 10 sub from Vera-Fi

I realize no links allowed - but this sub has won multiple Product of the Year awards even at $199 each 
 

Please give it a look

Best wishes - Mark 

I agree with @audiotroy's analysis.  In the bass region, the speakers are "seeing" a huge airspace.

Also, eyeballing Stereophile's measurements from June 1999, the Amati is not a bass monster.  Its efficiency is on the high side, and (for a given enclosure size) there's a trade-off relationship between efficiency and bass extension, so "not being a bass monster" is no surprise here.

The slope of the Amati's low-end rolloff is fairly gradual, which to me implies that it might have been designed for fairly small rooms and/or placement close to the wall so that it would benefit from the resulting complementary rise in the bass region due to boundary reinforcement.

@torke, I suggest you enjoy how they sound with the subs and not worry about the fact that they "need" subs.  Imo that's just the nature of this particular beast in what is effectively a very large space at low frequencies.

Duke

speaker manufacturer