Sounds noticeably better how? I haven't tried balanced on the SP1000M yet. But on the SE100... there is hardly a difference (provided SE output can drive your IEMs/phones with enough headroom left). The only noticeable difference on the SE100 was that the SE output seemed to have just a touch more low end than the balanced, with my Westone W80... and even that was so slight, I may have just imagined it.
One of the best DAC/headphone amps out there, Benchmark, only uses single ended, and publishes their reason for doing so over using a balanced headphone amp.
Balanced headphone outputs over single-ended is highly overrated, IMO. I find much more difference between a Moon Audio Silver Dragon versus a Double Helix Cables Silver Litz v3, than the difference between a quality single ended versus balanced headphone out.