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

@torke audiophile speakers are more about accuracy and quality of bass rather than quantity. I don’t know if this is your first pair of high end speakers. If you need bass that rattles walls you need subwoofers and you don’t need expensive speakers. Otherwise you will get the right amount of accurate bass with your current SFs. 
 

Also one other thing to note - your Nordost Heimdall 2 cables don’t do you any favors in the bass department. Once again, these cables are about accuracy and transparency. 

Also not a Nordost cable fan, except for digital.  They do nice digital cables.  Anyway, they do trend towards thinner sound.  My non-custom made cables are Decware and Duelund.  Yes, Decware.  Duelund makes very nice simple speaker cables.  Cheers

@celtic66 all about synergy. I run Nordost Tyr 2 XLRs, Frey 2 power cord on DAC and amp, Heimdall 2 power cord on streamer. Accurate, fast, transparent and dynamic. Combined with Audience FrontRow speaker cables just excellent synergy. I wouldn’t run Nordost Heimdall 2 interconnects and speaker cables in the same system though.

In over 25 years in high end audio, and owning several high-end, full range speakers, I never experienced any speaker, in any of my rooms, that exhibited a lack of bass.  If anything, the speakers sometime exhibit just the opposite, too much bass.  Also, I never experienced having a set of speakers that were internally wired incorrectly.  Sounds like a room, associated equipment, or a combination of the two issue to me.  Happy listening.          

Are your speakers new? If so, as others have suggested you may need to give them a little time to break in. If that’s not the issue, what speakers did you own before these and were you satisfied with the bass performance? if not, it’s possible that your personal preferences are such that subs will be necessary to meet your expectations.

did you buy the speakers from a dealer in your area? If so, and they are relatively new your dealer should help you with this problem. Maybe he could bring different speakers or a different amp to your room and experiment.  As others suggested, these are quality speakers, which should make enough bass, but “enough“ is subjective and you have too much money invested to be dissatisfied. If you bought them from a quality dealer, you should have a partner in solving this. Good luck.