"Power" isn't really the issue. Certainly, most interfaces can offer enough wattage to cause ear damage, theoretically.
However, the actual power is not determined by the HP-output alone, but by the headphones' own impedance as well: if it's substantially larger than the output impedance, then
P = U2 / Z
where U is the (RMS) output voltage of the interface; this is really the relevant parameter of a headphone-out's performance. Now, 300 Ω is a pretty fat impedance, so this means you need a higher voltage to get the same power than you would with lower-impedance headphones. You should definitely not expect very loud volume range when connecting these phones to an ordinary interface; in particular USB-powered models have a tendency to not offer very impressive voltage. For a FireWire model like the Saffire-Pro however, you can expect more generous output.
Definitely the headphones will work, the only question is whether they'll be loud enough for you. High-impedance phones aren't really meant to be driven very loud anyway, so if you need it loud another pair might be more suitable.