I replaced the seal beneath the fill valve and the seals for the bolts that hold the tank on the toilet. The leak is still there, and it is definitely coming from the hole for the fill valve.

Having already replaced the seals, will replacing the entire fill valve help?

Can't hurt, Benny. A new fluidmaster fill valve only costs about $8.00 so swap the old for the new and you should be all set!

Read the instructions provided with the fill valve for tightenss, etc. ;)

Also, just in case you have a crack there at the fill valve get up real close to the hole fill valve hole in the tank and inspect for cracks. If you think this could be an issue in any way you can accentuate anything questionable by adding food coloring to the tank and seeing if the "crack" gets colored. Obviously, if you have a cracked tank you will need to replace it.

Mark