timestamp output as seconds since epoch?

I need to grab the pgsql timestamp as an integer (seconds since epoch) 
in order to compare the dates programmatically later on. What I'd like 
is:
SELECT CAST('12/12/2004 4:50:45.3' AS TIMESTAMP)::INT8;
The docs talk alot about date input but only discuss the 4 SET 
regionalized date output methods. Thanks!><><><><><><><><><
AgentM
agentm@cmu.edu