Any USB/Ethernet controller suggestions?

[A_Camera]

That makes sense, but I'm sleightly confused about it not giving a max value for amps.

The maximum amp value never really matters, if you use a power supply with more amps output than needed it will still only output what you are using, and in this case hardly anything at all. In current the minimum amps is what's important, in voltage it is the exact voltage level, or the maximum, what matters. Maximum voltage matters because if you are using a power supply which gives more than 5V then it may fry your UC300/400.

So, if you have a power supply which provides 5V (maximum) and 500mA (minimum) then you are OK, but if you have one which gives you 5V and 25A then you are still OK, nothing bad happens.