You will need a preamp or channel strip to amplify a microphone signal to line level in order to input it into the Indigo card. You may also need such a device to provide phantom power too.
Personally I went for an M Audio Firewire 410, as I use it for live performance and didn't want to have mini jack connectors. I am also finding the 8 outputs very useful and have used the built-in preamps on occasion. The two (non-independant) headphone amplifiers are great for pre-listening in Live whilst also sending a click to the drummer. It is nice not to have to use a seperate MIDI interface as well and I find I have less issues with MIDI on the 410 than when using my USB MIDI interface.