WAL and TMP directory locations

I suspect that I already know the answer to my question but I'm looking
for confirmation from experts. I have moved my pg_xlog and pgsql_tmp
directories to a separate disk array to distribute IO. Some details...
Windows XP64, pg 8.3.7, all disk arrays are direct attach to my raid
card (SAS).

I have one rather large table (~1.5 B rows) that I do sorting and
grouping on in order to calculate some values that I need and then
insert those values into another table. This produces a lot of tmp
files (over 80 the last time I ran the query) which is why I moved the
tmp directory.

Question... is this appropriate and is there anything else I could
change to help speed things up.

Thanks,
Bob