Preamp gain vs. poweramp sensitivity

Hello,

Just purchased an Art Audio Carissa which has input sens. of 600mV (very high). At first, I was thinking that I would want a high-gain pre because the Carissa puts out only 16W/ch and could benefit from some preamp gain.

However, I believe upon considering the sensitivity that a high-gain pre is NOT desired because:

1) I would need to open the VC only a bit before the Carissa was driven to full power.

2) For the above reason, the high-gain is wasted anyway because the pre wouldn't be able to put out what it's capable of without overdriving the Carissa.

Do I have this straight? The relation of gain to voltage is not clear to me. The preamp is specified as outputting 2V yet, with a standard 2V source, that is actually unity gain! So what exactly does "20db of gain" in a preamp mean?

Thanks for clarification on this question.

Paul