Sorry Martin, should have been clearer on my usage plans: I'm only interested in optimizing for single-connection, sequential high-demand queries, so I think I'm safe bumping up memory usage, even if it's usually a disastrous idea for most users. I'll definitely check with the Enterprise folks!
Amul: thanks for the followup! Unfortunately, setting locally faces the same limitation as setting things in the config file -- I get an "ERROR: 3072000 is outside the valid range for parameter "work_mem" (64 .. 2097151)
SQL state: 22023" problem if I set above ~1.9gb. :(