It's possible for me with my DIR-655 and DI-624! If I'm hearing correclty, that is.
I connect my Wii, DS', and 2 Linksys media extenders, wirelessly, to my DI-624. Then the DI-624 to the DIR-655, wired to each other, for internet access.
I've had it this way for a year now. Just run a cable from any port on the DI-624 (not the WAN) to any port on the DIR-655 (not the WAN, duh).
Under Wireless, set a channel, making sure it's different from the DIR-655 (I use 6)
Under WAN set a Static IP Address (I use 192.168.2.2)
Under LAN set the IP (I use 192.168.2.20)
Under DHCP, turn off DHCP in the DI-624
And you're good to go. Is this what you're talking about?