Balanced outputs vs balanced design

Balanced interconnects between preamp and power amp are inherently less sensitive to noise pickup in the wires...that's why the pros use them for long runs. However, in the typical home environment with relatively short runs good quality single-ended interconnects don't have a noise pickup problem.

As for balanced circuitry in the power amp the advantage over single ended is largely theoretical for well designed equipment. It is often said that balanced is quieter because the signal is twice as strong, but there is also twice the circuit noise. Common mode noise, as for hum from the power supply, will be canceled, but there shouldn't be any such noise in a good unit.

I have balanced interconnects in my system, but only because the equipment I use has this interface. I think you should select your equipment on the basis of how it sounds to you. Balanced configuration has some advantage in certain cases, but, IMHO, it is sold, at considerable cost, to audiophiles who don't need it. It mainly gives you bragging rights.
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my favorite fully differentially balance equipment is maid by montana audio

I own a ARC Ref 3; it is a fabulous differentially balanced linestage, with loads of finesse, micro and macrodynamics; I suspect it will match very well to your Halcro. . I am also exceedingly partial to amps manufactured by Jeff Rowland Design (JRDG) like the Concerto. I have heard it matched to several Rowland power amps--which like yours are class D switching amps--and the results are supremely musical. . . . and yes, Rowland preamps are all completely balanced designs.

Eldartford is correct; choose your components on sound alone, not whether or not they are balanced.

Some of the finest high end manufacturers build only single ended equipment.

An other linestage I have enjoyed very much and may in fact soundly slightly sweeter on the Halcro MC20 than Ref 3 is the VTL 6.5 Mk2 hybrid. . . still a truly balanced design and truly magnificent. Were I now in the market for a linestage I would consider this device extremely seriously as well.
By the way, tell me more about your experience with the MC20: Strong and weak points? what other amps did you consider? Any other digital amps in the race? What tipped the scale in favor of Halcro MC20?