I would suggest that if your network includes a router for internet access, as most home networks do, that the DHCP server in the router be used, rather than the one in the NAS.
Wiggs gives one very good reason, I'll give you another ...
In most cases, the DHCP server, in addition to providing an ip address, also provides other important optional details such as the DNS server and gateway addresses, which are not required for a local area network to function, but are required if you want internet access
The DNS-323's DHCP server does not allow you to set any of these options (other than the length of the lease), so if you used it, rather than the router's DHCP server, you would have to manually set these entries on every PC on the network.
Additionally - in most cases - home networks do not have a DNS server, but use the ISP's DNS server, and the addresses of these servers can change from time to time, literally at the whim & fancy of the ISP, if you use the DNS-323's DHCP server with manually configured DNS server & gateway entries, you might not be aware of a change made by the ISP and suddenly find yourself unable to browse the internet.
On the other hand - your router, assuming it's getting it's WAN ip address from the ISP, using DHCP, will be automatically updated when such changes are made, and will in turn, automatically update the PCs - and the process is completely transparent to the end user.
The DHCP server in the DNS-323 appears to be a very basic one and suitable only for use on the most basic of networks - one with perhaps, the DNS-323 and a single PC.