I miss the smell of hot thermal compound in the morning
I believe the fave stress test at the moment is one of the linpack derived ones, of which there are several versions floating around. The claim is that linpack ones can find failures quicker than prime95, and will get things hotter faster too.
I believe Linpack will more likely uncover ram or northbridge related stability issues as it uses a very large data set and will stress the memory interface heavily. Prime95 tends to work on small data sets which will substantially of not completely fit in the CPU's cache and therefore stress the CPU itself more, but less the interfaces out. Personally I tend to do runs of prime95 AND linpack just to be absolutely safe.
Also I'd run memtest86+, at least 3 passes. That concentrates on the ram specifically which you should do as well particularly if overclocking that. I've been bitten before by a minor instability eventually tracked down to an obscure memory timing where the bios defaults were unstuitable. It would pass single runs, and might only show up one error an hour, but that is still one too many.