Importance of Impedance Matching

Just to chuck in my two pence worth as well - remember that it's the rise time of your signals (i.e. spectral contect) not the actual frequency of the signal which determines whether you need to do all of this. If your tracks are short relative to the rise time then you won't need to worry. If they are long then reducing the output drive (as previously suggested) will reduce the rise time and therefore enable you to drive longer track lengths. If you're worried then stick pads down on the PCB for some series resistors at the source end and tweak the values if necessary.