How Do I Resolve An Impedance Mismatch?

On the GarageBandFAQ it states "...if you are using a Professional mic (such as a Shure SM57, etc.) with an adaptor plug, you have an impedance mismatch (The mic is Low Impedance and the Line-In jack is High Impedance). When a signal hit’s a mismatch it’s like hitting a brick wall, most of the signal is reflected back and does not get through."

It goes on to say, "There are a variety of USB and FireWire interfaces that will allow you to plug various kinds of mics into any current Mac. Another choice, if your Mac has a Line-In jack, is to use a Mixing Console. Plug your Mic into that, and the Console into the Line-In on the Mac. Small Mixers can be had for very little money. This small Behringer mixer is available for around $45 which is a pretty awesome deal on a decent product ."

Will the USB and FireWire interfaces resolve the impedance mismatch? Will mixers? Also, I looked at some of the products listed on the GarageBandFAQ page, and I know microphones plug into them, but I couldn't figure out what kind of outputs these devices have. Are they all 1/4 inch? Do I need to get an adapter to convert 1/4 inch to 3.5mm?

Thanks.