I've done a bit of research into this myself, due to dissatisfaction with playing an electric fiddle (as yet unresolved...!!) and the advice I've been given is that if you are wanting to put anything into a headphone which could have volume spikes (either feedback or clicks from things getting unplugged by mistake, for example) then you need to have some protection to cut off the sound over a certain level otherwise you risk damaging your hearing. Not being technically minded I've never worked out if this would be something you'd need to worry about if it's just your own instrument running through a small pre-amp...

presumably in your situation though you might need the whole mix into an ear phone, not just yourself, otherwise hearing the rest of the band over the sound of yourself in an earpiece might be tricky if your hearing is a bit restricted in the first place? And if you were running a whole monitor mix into your ear piece it is more likely you'd need some of the protection I mentioned...?

Good luck though, I'll be very interested to hear if you come up with a workable solution!

Jess