Is a preamp necessary if my input will always be from a higher-quality DAC or CD player? I read somewhere that most CD players will drive most amps just fine without the additional gain from a preamp. is this really true?
Sometimes it works, sometimes it doesn't. Not all DVD/CD players have enough output to drive an amp to full power. Conversely, some amps have comparatively low gain and don't work well even with moderately high output CD players.
The only way to find out is to try. Just make sure you rig a temporary volume control. It doesn't have to be super high quality--just enough so that you can turn it down should it be too loud.
Depends on the poweramp but most poweramps have high enough gain to be used without a preamp. I use a passive preamp and have seldom the volume-knob turned past 12. But unless you have volume control on the cd player you will need a passive preamp to control the volume.
I agree with Tobbe. Most high quality CD players can drive them, but make sure there is a volume control. If you dont plan on using a turntable, headphones, or other device, and dont need the gain, then a preamp is just another device in the signal path and can be done without. But the only way you can know for sure is to try it!