Installing NWDI

Hi

We are planning to install NWDI .i am bit confused about the installation . we have a separate portal(AS Java Only) .should i go with DI Add on with SCA`s(SAPBUILDT,DICMS,DICBS and DIDTR) or with a separate system system only with NWDI(DEV,QAS and PRD) . if our developers develop in NWDI how can

we trasport those to the portal servers(DEV,QAS and PRD) . do all the above servers need to be in the same

SLD To do the trasnports ..