PLAN B analog blog

I have a euro system ( with more Plan Bs on the way :-)  ) I am going
to buy the headphone module, also looking at the Model 33 or 9...To my
thinking they both perform the same basic function ie attenuation/
mixing. I understand the 33 has the voltage control attenuation but
isnt it really all i need to mix say 3 sounds to then go out to the
M40 headphone ?  

ie 3 sounds into Model 33 to headphones 

or

3 sounds into model 9 to headphones