How Things Work
The world of Pro Audio is unlike the one found in a Home Theater, and I don't just mean the price. In fact you can typically find high quality pro audio equipment for less than similar high end home theater systems.
The difference as always is in the details. Balanced vs. Unbalanced, Analog vs. Digital, +4dbu vs. -10dbV; I'll try to explain what it all means in a way that you might be able to understand.
First: Volumes and Frequencies