ORDER BY and LIMIT with SubSelects - Mailing list pgsql-performance

I need to get 200 sets of the most recent data from a table for further
processing, ordered by payDate. My
current solution is to use subselects to:
1 - get a list of unique data
2 - get the 200 most recent records (first 200 rows, sorted descending)
3 - sort them in ascending order

SELECT SSS.* FROM
 (SELECT SS.* FROM
   (SELECT DISTINCT ON (nonUniqField)
    first, second, third, cost, payDate, nonUniqField
    FROM histdata
    WHERE userID = 19048 AND cost IS NOT NULL
   )
  SS
  ORDER BY SS.payDate DESC LIMIT 200
) SSS
ORDER BY payDate;

My question is in regards to steps 2 and 3 above. Is there some way that
I can combine both steps into one to save some time?

PostgreSQL 7.4beta2 on i686-pc-linux-gnu, compiled by GCC 2.95.4

Thanks
Ron