You won't find any stock just these that could possibly oc to 120hz. http://www.blurbusters.com/overclock/120hz-1440p-ips-monitors/ You may just need to forget ips and go with tn if you want 144hz.
What you have now is most likely tn as most lcd monitors are tn. If that's fine as far as color and viewing angles then your are fine with tn. Especially for gaming, tn will have higher hz models.