In the T5810, you'll want to go with the E5-1620*. It's 4-core, dual thread. The E5-1603/1607 are 4 core but not dual threaded.... and run on slower RAM. The 1620 costs more but benches ~90% higher than the 1603. However, if you're buying from Outlet, you can watch to see when a 1620 unit is...