RAC h/w basic costs

We are planning to move to RAC from single node database, as a start we want to migrate to 2 node RAC and ASM. Management asked us to present basic starting costs involved so that it helps in the decision making process. We already have some servers in place, we might require SAN, HBAs and hardware for constituting interconnect(NICs/Switches etc) . I am not sure where to start, It would be great if anyone had similar experiences and can share accross. We have evaluated Oracle licensing costs, am only looking for the above said h/w costs. Below are details of our environment, I can provide more details if required.

Database version: 11.2
Size: 500G
OS: RHEL 4
Servers: Dell servers with 2 Xeon Quad core CPUs. Type: R12 ERP database

Thanks in advance,
Venkat.

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