How much memory is required for an Oracle connection/process on Unix(hp-ux)?

I am not sure whether it is the right forum but I want to know if any one has experienced this kind of problem and may provide guidance/suggestions. I have a new HP-UX server on which I have installed Oracle 9i. On a small database of SGA around 150 MB, each oracle process(dbwr,smon etc.) and a sqlplus connection takes around 20mb memory (RSS) according to Glance software.
As the number of connections increase by 10 the subsequent and current processes
consume less memory (each 15mb apprx.), less than before but even then it is more than expected.
As I increase the SGA size around 350 Mb, each process RSS shows round 50mb, so ten processes including required Oracle processes consume around 500 Mb which is too high. As I increase the no of sqlplus/TOAD connections by 10 the subsequent and current processes consume less memory but not significantly less that it may sustain 300+ users on the system. The Pga memory consumed by each process shows very less thru V$ views. I have 8Gb memory on the server out of which free is around 5.1 GB without any database started.
The memory consumed by Unix kernel- Sys mem is 1.7GB as per Glance which I think is also very high.
Please let me know your suggestions.

Thanks in Advance.

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