YOU are the weakest LINK. Good BYE!
Maybe try some new cables.
Maybe try some new cables.
As far as I know your pre has two sets of outs that you can use at the same time.
You can get SS BAT VK500 to drive the bottom if your speakers are bi-wireable. You will need an attenuator passive or active to tame the gain of VK500.
If you don't have a budget for BAT along with attenuator you can get McCormack DNA1.
Whichever amp has larger gain that is the one that needs extra volume controll in the path and so is extra pair of interconnects.
If you don't have a budget for McCormack either you can downgrade your cables to build the system that will for hell shure bring you the bass you desire even with RadioShack wires.
To answer some of your questions, the room they used to be in was slightly larger (19x14). I got more bass driving them with PS Audio HCA-2 or Pass X-350, but tube is ultimately what I wanted and settled for. Listening position was also tried, but at 3' from the wall, it had worked well for me for the past several years.
Yes, two dedicated AC lines with power filter feeding CD and pre, power amps are plugged straight to the wall. No bi-wire capability with Sonus Faber, so one pair of amp is all I can use (thank God).
Sounds like wire is what I should replace? I had very good luck with JPS Superconductor 2, but they were so stiff they broke one of my input on the SF Line 3 SE. What else is out there that won't sacrifice the air/speed/transparency of Diamond X3 and still give me more bass?
Semi, before you buy expensive cables I encourage you to experiment more with placement. In my experience your listening position should be further out into your room, like 4 to 4 1/2 feet (sort of matching your speakers). I would buy a Radio Shack sound level meter and a test disk (you need also to get the corrections for the bass numbers - its mostly down under 60 hz) and chart out different locations for speakers and listening position. In my 19.5 x 13.5 ft room I found mine at 25% into the room for speakers and listening position). Also, you don't mention side wall distances - you will get some reinforcement from that placement as well. You might look at Rives site and plug in your room dimensions and see what that would recommend. IMHO, while cables might make a difference, it will only be a subtle one.
I second the thought on placement. I have been trying different ones over the past three years and have only just found what I consider the best so far. The second-last try imaged well but had a midbass hump and no low bass; a new placement took care of both. Frustratingly, the latest greatest speaker position was an accident--happened because kids overnighted in the listening room and the speakers had to be moved. Never underestimate the value of kids.
Getting the rack out of a corner node helped too.
I'm with Marakanetz. The Amanti's have possibly the best sound I've ever heard from about 100 Hz up, but they quite simply don't have much bass. IIRC, they only have two 8" woofers, which just doesn't get it done for me.
Other than adding a sub or changing speakers, you might consider a SS preamp first and possibly a SS amp as well.
But as good as the Amanti's sound, they just don't have enough authority for me, and it doesn't sound like they do for you either.