Yes the sempron is replacing the Duron, but there are 2 versions of the sempron, one is a socket A , version and the other, the socket 754, the 754, version is a dumbed down version of the A64. If you are looking at a Sempron, go for the 754, as it gives you the upgrade path of the A64. If you plan on doing that, you just as well go for the entry level A64, which is the A64 2800, the price difference between the sempron 3100 and the A64 2800, is negligible.