Surprised you can't hear it, open your window LOL
ANYWAY...
Trying to compare the 400 to the 700B is sort of fruitless. I could go through the corksniffer approach and test different speakers and music sources but in the end it will come down to this
I give the nod to the 400 just barely for overall sweetness of sound and soundstage so far but I think that is the FC talking there. The 700B has the headroom in it's favor indeed as well as what I believe to hear is a slightly fuller bottomend. It also has twice the power so no competition there. With the FC setup, it will shine just as bright as the FC 400s in sound as Lee has already raved about. I love them both, best damn amps on the planet
This amp just whispered to me that she likes it here and wants to stay, she's tired of being shipped around like a mailorder bride and she digs dudes with longhair that play Explorer's and drink Dr Pepper