I use a focusrite saffire pro14. It is a firewire interface that cost about 250.00 $ I have had no problems with humming or delay. I use it to play chords with a guitar, then I accompany myself with a bass. From what I learned about this when I bought the thing, USB is slower and will give you delay troubles.
Firewire is no longer the top of the line cutting edge, they have LAN connections for rich people. You have to be careful when you buy a unit though. Some of them get power through the connection to the computer. If you have a connection to support this it's all good. If you don't, make sure you get a unit with an external power supply.
It was a bold person who first ate an oyster.