All depends on what chipset ur using, P31,P35,P41,P43,P45 generally run a lot cooler then X38/X48.
It also depends on what sort of cooling it has on it allready, if just a standard normal heatsink then maybe a better aftermarked one may be better.
But if you have heatpipe cooling on the mosfets, and chipsets, that should be more then enough.
As an example my Msi P35 Neo2 FR, uses heatpipe cooling so a lot better then just standard heatsinks, even when im really pushing my mobo, with 500+ fsb, and 1.4/1.5v on the north bridge, iv never yet seen it go above 40c.
Generally temps range from 30c all the way upto 60c depending on chipset and cooling of it, so unless ur going well over 60c i would'nt worry.