George , I tried to PM you, w/o success. If you could PM me,Done.
Looked it all up, and your right to go for the Lightspeed in this system.
Your Adcom with 78ohm output impedance at 2.1v is a perfect match.
Your Nuforce at 51kohm input impedance with 0.45v input sensitivity for full output, is also perfect.
As you can see you only need 0.45v into your amp to give it's full wattage output, and you have 2.1v from your source, so you don't need an active preamp adding more gain.
Remember what Nelson Pass said.
Nelson Pass,
We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.
Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
Cheers George