Increasing gain for your vinyl front end when pre-amp doesn't quite have enough juice

In my opinion we are trying to out a square peg through a round hole. I would recommend a system turnover which my require obtaining some used equipment here or on the other well known sites to get you speakers and a system that can do the job you want.
You mentioned your dream speakers were Vandys at $8400. For a fraction of that price you can get the Magnepan LRS which I heard At AXPONA and are a flat out deal at $650 or the .7i or 1.7i (which I own). If you get the .7i or 1.7i, then for less than $600 you can get the MyeStands which will improve dynamics and bass. I used to use a sub with my Maggies. Since the MyeStands, I am selling my subs. For the LRS you may need a sub. Get a small sealed sub. REL or Rythmikaudio. As for an amp, get a used solid state relatively high watt class AB or low watt high bandwidth class A stereo or integrated amp. For Maggies, I prefer the former. If you go with a higher sensitivity box speaker you can go with either. What ever is cheapest but good. That is where the most money is going to go. You may be able to keep the Mani and Saga. But those will be the weak links in your system. Sell the Behringer and Vandys. Yes it’s a partial system overhaul. Welcome to audiophile land!

Listen to @almarg . Try a new preamp. You could also buy a second power amp and run them as bridge mode monos.

@almarg 
The maximum output on the Saga is 10 volts. Can you please explain what that means as far as driving a power amp?
Thanks much
Yogiboy

More about Zu Audio (a very high efficient crossoverless speakers).  
The prices and their trial policy is incredibly good for what you can get. 
These speaker can be driven with 5w amp in the big room. 
Life is so much easier with 101bd sensitivity speakers. 

@yogiboy The ">10 volt" maximum output spec of the Saga means that it is capable of putting out more than 10 volts before it will clip, when its active mode is being used. (In passive mode there is presumably no practical limit to its maximum output voltage). The output voltage it will provide at any given time, though, **if its volume control is at max,** will equal the input voltage provided to it increased by its gain. And in this case the gain of 0 db means that the output voltage will equal the input voltage.

I’ve seen several instances here in the past in which very large preamp output voltage specs (e.g., 10 or 20 volts or so) have misled people into thinking that is what the preamp actually outputs, rather than representing maximum capability before clipping.

Looking at the specific numbers in this case, the 42 db gain setting that was originally used on the phono stage (which is typical of gain settings that are used with moving magnet cartridges) corresponds to a voltage multiplication of 126 times. When the cartridge is putting out the 4.5 mv it is rated to put out under the standard test conditions the 42 db gain setting will result in an input to the preamp (and an output from the preamp if its volume control is at max) of 126 x 4.5 mv = 0.567 volts. Since the power amp only provides balanced inputs, it will interpret 0.567 volts provided to it in single-ended form as 0.567/2 = 0.28 volts. That is less than 1/4th of the voltage required to drive the amp to full power, **and will only occur with the volume control set at max** if the cartridge is putting out 4.5 mv. (Although the peaks of some recordings can cause the cartridge to significantly exceed the 4.5 mv it is rated to provide under the standard test conditions).

The bottom line here, as I see it, is that phono stages are generally designed with the expectation that they will be used with line stages providing significant gain. And in this case the line stage provides the same gain as a passive preamp, namely none, which will result in exactly the issue the OP described with many and perhaps most cartridge/phono stage combinations. So IMO the root cause of the problem should be fixed, before other changes to the system are considered.  That said, though, it does seem possible that the 48 db setting of the phono stage could prove to be satisfactory.

@noromance Thanks for your comment.

Best regards,

-- Al