those are the only ones you should need to play with in 7.1.3. Here -N and -S are probably fine as they are. You'll know if you need to increase -N b/c you'll see nsd complaining it can't connect in the log. The sort memory specified in -S is per backend, not shared, so making it large "just in case" isn't a great idea. 2M is plenty for most uses. With -B you should make it as large as you can w/o causing other stuff to swap when PG is under load.
