Siebel Application Server Sizing ?

Would anyone in the community have experience in the sizing and high level costing of Siebel ?

I am in the position currently of proposing a suitable infrastructure to support Siebel eHealthcare vertical (versions 6 & 7), more specifically I am trying to identify how the infrastructure can be scalable, resilient, geographically distributed and still perform well.

If anyone could provide guidance, pointers or ideally an answer, I would be most grateful.

Regards,

Tony...