Wow, thank you very much for all the inputs. It seems all the parameters affects the gain, and it sounds like really my system is lacking synergy. And there is alot of technical stuff that I don't really understand, please excuse me if I ask something stupid.
It seems the gain of the amp is not a published specification. I can only see it inside the Stereophile review under measurement section. How stupid ...
Almarg, thanks for your insight about bass roll off with attenuator. I don't have the engineering background to understand the correlations between impedance and all those stuff, but I will take your words.
I really want to keep the PrimaLuan preamp. I don't have anything technical to back me up, but in my experience, the preamp has a bigger impact to the sound then the amp. And I like how PrimaLuna sound, so, I likely will keep it.
I will try to connect the DAC directly to the amp, but I will missed the PrimaLuna sound.
About the option to lower the gain of McCormack, I think I won't go that path also. It seems I will need to send the amp to Steve, it is kind of a hassle. Also, my new Zu speaker won't need such high current, so, if it is not compatible, I may sell it out and get something else.
As people can see, my Maverick DAC has a volume control as well. So, I can lower my DAC input so I can make the volume know of the preamp within a usable range. This is similar to if I lower the volume in iTunes. My question is, how would this affect the sound? Will I run into the bass roll off problem like using attenuator?
Another option is to get another amp. I would like to try the SET amp. If I want to keep the PrimaLuna, what parameters should I pay attention to? I know most of them are pretty low power, but as said, power is not the real problem. I don't think they publish the gain info. Also, does the requirement to have input impedance > 100k Ohm still applies? Maybe more straight forward, what is your recommendation?