Don't turn off fsync if you value your data! It's very necessary and if you turn it off you're losing all the data integrity attributes of using a proper RDBMS.
With 384MB of memory you can increase sort mem size well above 2MB, even, though that suggestion is much better than the default.
But the shared buffer pool must be greatly increased. It's mentioned above but the importance isn't stressed. Postgres, by default, only caches 64 blocks in shared memory and with that much memory you should increase the size to a much larger value.
Randy's suggestions are good, too - don't make things objects unless they need to be, which normally implies you need the auditing information built into objects (creation time, user, etc), you need to explicitly manage permissions on the object etc.
We don't use Postgres inheritance because it is broken, in essence. There's a document lying around in file storage that explains why, the reasons are many.
