DXS questions

I've got

3 CD (90ES, 250 and 300 ) for 700 CDs 1 DVP-CX850D 1 MD ( 2 TOS In 1 oax In one TOS out) 1 DSS 1 LD 1 Receiver ( Sony STR-DA90ESG )

So I want to order

1 ea 4TOS in 1 ea 2TOS/2RCA in 1 ea 4 TOS out 1 ea 2TOS/2RCA out

1) Question arose in my mind as to the Dolby Digital from DVD.

Would I have to turn DD off when I use DXS , or will it pass DD as well.

2) Do I have a need for the Stream processor module at this point ( No situation where SCMS is in the picture right now.)

3) Will the future DSP do SCMS manipulation also, or will I need the stream processor then to manipulate the SCMS.

in other words is the tream processor a necessary module for the future?

Sinan