they may or may not get you to 4.0(those timings are already pretty loose so i wouldnt bet on it tbh).most 2gb modules dont clock very well compared to 1gb modules.so its very much luck of the draw.if you want guaranteed headroom youd have to bump up to pc27200/8000 to guarantee a 4.0 oc.like meionm said you may want to take a look at the gskill 2x2gb kits.specifically the 8000s.