If at all possible, you want to let SBS hand out DHCP requests, not your
The advatange of letting SBS do the DHCP role is because DHCP, DNS, AD,
Exchange and IIS are all tightly tweaked to work in the SBS environment, and
the SBS management console and wizards work and assume that SBS is handling
all the roles it was designed for.
See Susan's blog for more info:
Kevin Weilbacher [SBS MVP]