Upgrade Maudio FW410 or Buy a Headphone Amp?

[kjs]

I have a pair of DT770 Pro 250 Ohm and I feel my M Audio FW410 is not powering them well enough.

I know the FW410 is pretty old now so I am wondering if I should upgrade it or buy a headphone preamp.

I only use 1 pair of headphones and 2 monitor speakers 1/4 jack - I guess having 1 mic input would / could be handy.

So advice on either what HP amp to buy or what Sound Interface to buy would be most welcome