Do I need a preamplifier?
You can use a preamplifier if you prefer, but it is not necessary unless you are using a turntable. Then you would need a preamplifier with a phono stage to bring the signal up to line level. If your source level is relatively low, then a preamplifier can help ensure a strong enough signal to drive the amplifier to full output power. If you have multiple sources and would like to switch between them, then a preamplifier is also a useful way to do this.