Well, let's give it a try. I'm sure someone else may have better explanations for some, but let's see if I can help...
1. Noise floor. refers to the level of noise audible when your system is on and nothing is playing, or the noise inbetween songs, or the recording itself during a quiet passage.
2. Head room. refers to having "a little extra in reserve". Sometimes used in reference to wattage, but not exclusively.
3. Leg room. umm... not really sure, but may be similar to number 2. Or how much room your back seat passengers have to stretch out their legs?
4. Bottoming out. usually in reference to a speaker achieving its maximum extension and audibly distorting.
5. PEQ. Parametric equalizer. A type of eq where the user can select the frequency to adjust and how "thick" to make it. (also known as the "q"; basically how much of the adjoining frequencies will be affected.)
I hope that helps somewhat... and hopefully I'm correct on what I've written.
sleeper
Oh, and if your sub doesn't have a PEQ, you can run one, or any other form of equalization, inline from your receiver to the sub.
