If you are buying an espresso machine, you will NEED a coffee tamper. While stovetop espresso is a boiling-temperature extraction done at fairly low pressure (2 bars), espresso machines use slightly lower temperature (195-200 degrees) and much higher pressure (9 bars). To do a satisfying espresso extraction at 9 bars requires that the coffee grounds be finer, and that they be densely compacted.
We carry a large range of coffee tampers. Most espresso machines have portafilters that are 57 or 58 millimeters in diameter. A small number of espresso machines, and all lever machines, use smaller diameters (from 48 to 53 millimeters). Make sure that you choose the correct size when ordering.