Other solution would be using a mini mixer as "afterburner" for headphone output. But this seems a little bit oversized to me. Eventually there is a cheap and handy (pocket-)headphone amp ?
My setup only uses a DI-box for FOH and a small mixer for the drummer to be used as a headphone amp. If you need to get a separate headphone amp, this would indicate that the headphone function on the apparatus sucks and also defeats the purpose of using it. Rather use 2 items that work than 1 item that doesn't work
I have a question, how important is for the backing track to be stereo? Because I always thought that no one can really tell the difference in live situations.
For stereo separation it's not quite important, but hard panned element help for headroom.