Also the 4 channel inputs are still lumped together
which may give crosstalk problems. "
agreed, wires running parallel to each other forms a capacitor, that is the mechanism involved,
what i do in my builds is to use 2 conductor plus shield/screen cables, one for each input....
fyi, the sakura AV400 used a selector chip right at the input jacks so that cross-talk is not an issue..
jojod did a preamp build with relay input selectors sometime back...