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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