Guys, don't forget the stock touring leather seats have SEAT WARMERS!
Mmmmmm.... Hot butt at the touch of a button!
Touring + Sport
Like everyone said, if you're not modding the interior and you want it all setup turnkey, than the Touring trim is worth it. All things considering, the base is only 40lbs lighter and 40lbs can be made up VERY easily. Just changing the tires to lighter performance tires would free up that much weight (and would be a better weight decrease than any other part on the car due to outer spinning mass).
If you don't care about navigation, just know that the computer that comes with the touring trim has a LOT of really cool features... The voice command beats ALL the other systems I've used. I mumbled '106.7' and it changed the radio to 106.7 FM! It's pretty sweet IMO.