The Barnes X is one of my favorite bullets. While it is overkill for whitetails, it's awesome for big hogs. In my .30-06, I use PMC ammo loaded with 165 Barnes X and I have shot quite a few deer and hogs with it. With a 180 grainer, it's definately too tough for deer, but with groups like sub-MOA, it's okay...just don't expect too much expansion.
The newer TSX bullet is very similar to the original X except it has 3 rings for less stress on the barrel. People say that accuracy is more uniform with the TSX. In my Kimber Montana in .300WSM, it shoots about 1" groups (The Nosler Partitions shoot a bit better with about .50 to .75").
Still, if you are getting such good groups, then congrats on the load!
Zachary