Unless your headphone can't reach your desired listening volume when the amp is at max gain, then don't bother getting a balanced cable! There's no benefit. It's just a way for the audio industry to cash in money from naive consumers.
Also if you insist on using balanced, you must have a balanced cable, you can't just feed a normal cable and use an adaptor for balanced output. It has no benefit and will fry your amp. Although balanced cables can be used with unbalanced output.