Depends on what you want more. The Stealth will outrun a Conquest, but is most likely more expensive to insure. I have heard of similar problems with the Stealth as well. I admit I'm not an expert when it comes to keeping an engine cool but my advice is to put in a colder thermostat and possibly a more powerful set a fans for the radiator.

Just in case you didn't know, both the Conquest and Stealth are rebadged Mitsubishi products just as Patrick's Stratus is.