Are we talking cheapest?
If he wants a cheap mobo with sound so good, he doesn't need a sound card, then it's Epox 8RDA+. It's an overclocking champ in the $80 range.
Make sure it's the plus version.
But as long as it's an nForce2 mobo, he should be ok.
If he doesn't need sound, I would look into Soltek, + check this out
http://www.theinquirer.net/?article=10384
and this
http://www.overclockers.com/tips00427/
Increasing the FSB changes the speed of the whole motherboard and everything connected to it unless the mobo has a PCI lock.
The following nForce2 boards have a confirmed PCI lock:
Epox, Abit, Asus, Chaintech, Soltek, MSI, Gigabyte
It is unclear whether Leadtek nForce2 has a PCI lock.
VIA boards do not have a PCI lock.