Unison Research S6 or Leben CS-300F or Manley Stingray II???

Hello fellow audiogoners. 
I at a loss choosing between the three.
The only amp I have been able to audition in my system is UR. Sweet, nice, too loud for my taste (volume at 10AM was already too loud) ,  but lacking in openness and soundstage . 
Leben is said to be very nice and sweet and stuff, but it lacks remote controls, which is a downside in my case.
Manley Stingray, in my opinion, is very nice looking, and fits the bill in all aspects, except Stereophile treated it like an entry-level amp, lightly and condescendingly, if you know what I mean. It also rated the Stingray II as B class, while the other two were rated A.

I would very much appreciate comment from those of you who have had the opportunity to audition all three (or at least two of the contestants ).  My main question here is about the sound character and differences of these three amps rather than functionality.

Listening to the other two is not an option, unfortunately.

Source is CHORD DAC64, speakers are open-baffle speakers of local manufacture, rated at 93dB and 4 ohms. They are currently powered by a Hegel H300, but it sounds a little dull and uninvolving. 

Thanks for your opinions. 

It might be worth mentioning that I mostly listen to jazz (60%) and classical (30%),  so I do like my spaciousness and true tonality.  However,  I took liking to blues recently,  mainly Otis Taylor and Seasick Steve variety,  so good punch is very welcome. 
Although you asked about sonics rather than functionality, I’ll mention that if the UR S6 produces too much volume at low settings of the volume control I suspect that the Manley will also. 

The unbalanced outputs of your DAC have a "full scale" (maximum) output level of a bit more than 3 volts according to Stereophile’s measurements, which is quite high, and the Manley will be driven to full power by an input of approximately 0.2 volts with the volume control at max.  Which suggests that you would be using the volume control quite low within its range.

The Leben, on the other hand, is spec’d such that 0.6 volts is necessary to drive it to full power with the volume control at max, while at the same time full power is somewhat less than the Manley can provide.

You might consider addressing this issue with a pair of Rothwell in-line attenuators at the inputs of the amp.  Some users (including me) have had positive experiences with them, while others have reported that they compromise dynamics to some degree.  But I suspect that the relatively high input impedances of these amps would make a positive outcome with them more likely than not.

Good luck.  Regards,
-- Al
Thanks for your input.  I will definitely do as you recommend once I have chosen an amp.
Surprisingly,  the Hegel does not have this problem to that extent via XLR, although it does sound about 20% louder than,  say,  RCA inputs feed by line outputs of an OPPO BDP-105D.
You might want to also include LM Audio on your list.  

As for the remote control issue, I was originally skeptical about this with Shindo gear but having lived with it in my system for a couple of years it is really a non problem for me.  It is good to have nothing to think about but the excellent music you are hearing.  
Don't put too much stock in Stereophile. I have a Stingray II in a secondary system (with Merlin TSM and a Marantz SA-11s2) and find it very satisfying, especially after re-tubing with Psvane EL84. Never heard the others you mention, though.
Thank for your response, all.
Stingray II, unfortunately, proved to be somewhat hard to get (the seller is behaving rather strangely), although I initially decided to get this amp as its remote-powered controls are very convenient).

So I agreed with both Unison Research S6 seller and the Leben CS-300F seller to send them over to me for a test (unusual arrangement, but I somehow managed to agree this with them).

The S6 is in the house and I like it a lot, expecting the Leben to arrive. Will post my impressions on both.