How can I make this query faster (resend)

In the pictures table all the ratings have a shared index
 
CREATE INDEX idx_rating ON pictures USING btree  (rating_nudity, rating_violence, rating_sex, rating_racism, rating_spoilers, rating_yaoi, rating_yuri, rating_profanity);
 
and approved and date_submitted and user_id also have their own btree indexes.
 
In the picture_categories table pid and cat_id have their own btree indices plus one together.

 

Full table definition: http://pastebin.ca/57219

 

the cat_id and rating values vary from query to query. The one listed above took 54 seconds in a test run just now. Here is explain analyze: http://pastebin.ca/57220

 

 

Both pictures and picture categories have about 287,000 rows
 
This query needs to run in under about a second or it kills my site by clogging apache slots (apache maxes out at 256 and I can have several hundred people on my site at a time). How can I make it run faster?
 
 
Server is a dual xeon with a gig of ram dedicated mostly to postgresql.
Here is the changed lines in my postgresql.conf: http://pastebin.ca/57222

 

I know hyperthreading is considered something that can slow down a server but with my very high concurancy (averages about 400-500 concurant users during peak hours) I am hoping the extra virtual CPUs wil help. Anyone have experance that says diferent at high concurancy?