Connecting two routers

[#1]

I currently have two PCs connected to a Draytek Vigor 2800V router. This has a printer attached to the built in print server and an analogue phone attached the built in VoiP. I'm trying to place all of this behind a Netgear DG834 so that the Netgear is basically a modem, which routes everything to the Draytek.
I had a rummage through the Draytek forums and found this, where somene is trying to do the same but with a Cable modem instead of the Netgear.

Quote

Set a PC network card to dynamic IP to configure both routers. Make sure the PC firewall is enabled while configuring. First, configure the cable modem, disable it's firewall. Enable DMZ and point all to LAN1 port. Save configuration to PC and disconnect it. Second, connect cable router LAN1 to Vigor WAN. Connect PC to a Vigor LAN port. Configure the Vigor appropiately (sip etc.). ENABLE FIREWALL, disable DMZ. Connect PC's only to the Vigor LAN ports. This way, the Vigor can prioritize VoIP calls over other traffic and PC's are secure behind the Vigors firewall. Also, all settings can be controlled in the Vigor.

Is this right?
The manuals for both routers can be found at:
http://www.draytek.com/user/SupportDownloadsDetail.php?action=Load&MID=11&ID=16#PdInfo
http://kb.netgear.com/app/answers/detail/a_id/2066

[#2]

Why?

[#3]

@bojangles: I've looked into doing this in the past and came to the conclusion it couldn't be done. The 2800 series don't have a separate WAN port and the LAN ports are for local use only and the PPPoE client won't accept input through them. If you do find a way to do this I'd be very interested to know how as I've a 2800vg and a DG834 I'd love to introduce to each other! I suspect the person on the Draytek forum isn't talking about a 2800.
@zpeterk: possibly because Draytek DSL performance isn't the best.

[#4]

I am not an expert at connecting routers together but I would have thought that you would need to turn off DHCP on one of them.  DHCP (Dynamic Host Control Protocol) is the function that assigns an IP address to the devices you attach (if these do not have a fixed IP address).  If the master router is the one that runs DHCP then you probably want to set the IP address of the other router within the same range so you can communicate with it.