db server load

Hi All,
I would like to ask to you, how many connections a db server can handle.
I know the question is not so easy, and actually I don't want to known a
"number" but something like:
- up to 100 connections: small load, low entry server is enough
- up to 200 connections: the db server starts to sweat, you need a
dedicated medium server
- up to 300 connections: hard work, dedicated server
- up to 500 connections: hard work, dedicated high level server

I would like just to understand when we can talk about small/medium/high
load.

At the moment I'm using a quad-proc system with a 6 disk 1+0 RAID array
and 2 separate disks for the OS and write-ahead logs.

Thanks
ste