Does it matter what power amp i get?

Hi I am new to home recording. I have a pair of Alesis M1 Passive speakers and need to get an amplifier for them. I am wondering if (aside from the wattage) the type of the amplifier matters at all? I was looking at an alesis ra 150, its 200 dollars, but a friend told me any old amplifier will work, even a 100Watt one from radioshack (which I couldn't find anyway). But are there any recommendations?