What's a phonostage, and do I need one?

Help a newbie make the right decisions. I'm almost finished putting together my beginner stereo system. All I have left is deciding on my turntable. I've been looking at the Audiogon discussions and pretty much decided on a Music Hall MMF-2.1 or 5 (I'm leaning towards the 5). My system is powered by an old Marantz 2270 (70 watts). It has a phono jack. One of the discussion threads concerned someone whose phono output was only putting out 1/2 the volume of his other sources. My question is, if I'm using my old receiver, am I going to need to purchase something else on top of what is included with the MMF-5 (or 2.1) for my turntable to sound comperable to my other sources? (my other sources are a marantz CC3000 5 disk changer and an old Nakamichi tape deck.) Thanks in advance.