Your going to want the Core i3-2100. That CPU wipes the floor with pretty much any Athlon II or Llano out right now. Despite the fact that it only has 2 cores, those 2 cores kick some major ass. Add that ontop of the fact that anyone looking at Athlon II/Core I3's are not doing intensive computational work and the real victor is easy to pick.
I would look over this reivew:
http://techreport.com/articles.x/21730Thank use the 3650 as a reference for how fast the 631 is. I imagine you should come to the same conclusion.
Edit: It looks like that review doesn't cover the 3650, however judging that the 3800 gets stomped by the i3-2100 that should give you your answer. Also, for any amount the Llano can overclock, so can that i3. The difference being that the more you push that i3, the bigger of a performance gap there will be than an equally pushed Llano.