A front tire change should help, but I'll let those with non-stock tires weigh in on that.
Some members have filled the handle bars with silicon (get a tube at Home Depot, etc., lay the bike over and start squeezing it out a caulk gun. Turn bike to other side and repeat if nesiciary) and have commented on a noticeable decrease in vibrations. Since its a $3 fix it might be worth a shot. Thicker 'squishier' grips also help, check out the set ProCycle has on their TW page. I find my leather riding gloves (crotch rocket racing style) help a lot to reduce felt vibes and improve comfort.