The Yamaha AN1x Synthesizer mailing list

Excuse my ignorance once again, but how do you route the ins&outs of
a 
midi interface 
with more than 1 in&out ? 

let me set up an example-situation: 
Yamaha AN1x controlling an a3000 sampler 
and the sampler registers notes back to cubase (?) 
and three other soundmodules and another masterkeyboard 
and two 19" FX units with MIDI. 
How do you hook this all up? regarding the Ins & outs (midi). 

I'm thinking about getting the midiman midisport 2x2 or the all new 
4x4 

Maybe i'm just a little stupid with this, but it is mind-boggling ;) 
;P