Don't get intimidated. I remember my in my first thread that people were recommending that I buy all sorts of odd items (cables, paper, etc.).
Your source is what you use to listen to music, i.e. your cd player, digital audio player (ipod, etc.), computer/audio card, or even turntable/record player.
An amp is just that, an amplifier. Many members here use headphone amplifiers in order to get the most out of their headphone investment.
There are also modifications (or mods) that you could do to your headphones in order to adjust the sound to your preference. Some members here have done everything from changing the headphone cable to using wood for the reverberation chamber that the headphone driver sits in.
In order to get an idea of what we can do to help you, we need to know what you have. If it's a 5.5 generation ipod with your SR-125s, that gives us something to work with.
Let us know.
Nylan