Oh, I see. The original Athlon II X2,3,4 processors are a generation older than the Athlon X4's that you see today and they use a different socket (FM2/FM2+). (Confusing the way AMD brought back the Athlon name)
And the Athlon II you have is from the same generation as the Phenom IIs I mentioned. The main difference is the Phenoms come with an L3 cache and the Athlons don't.
But since this is for general use (non-gaming), you won't see a huge improvement upgrading you processor within the AM3 socket lineup unless you went to a 6 core Phenom II X6 1075, 1090, or 1100. Again, all obsolete. Usually only found as used...