Usually?..ish if you feel it in the seat it has something to do with tires. In the steering, something to do with the front end..ish. I'd replace the steering dampener while you're at it, get a good one $50-$70 and its a 10min job. Check the posts on them, but i'd stay away from the Joe TLC.
2004 SSB 6spd Coupe. Annnnd!....the Sun is Shinin!