You don't HAVE to have DHCP enabled on the D-Link. When you disable it, the D-Link essentially becomes a wireless access point. The wireless hosts will associate with the D-Link, and will be assigned addresses via the gateway router. You will have to make sure that the Gateway router and the D-Link you have now have IP addresses in the same subnet.
As far as recommended brands, everyone has their preference. DLink is my personal Fav, with Belkin & Linksys being on my no-no list... I had 1 belkin router, and it was a piece of garbage, returned it for a new one, had same issues, called tech support, and I knew more about the hardware than they did. I personally haven't had a Linksys, but have many friends & family with them, and constant network troubles. Current DLink network is flawless, except my girl is frustrated that when she closes her laptop for a few minutes, and re-opens it, she has to wait for internet to reconnect... :rolls eyes: