I was using two DIR-655's in the past in this config:
cable modem -> DIR-655 #1 -> Dir-655 #2 (in switch only mode)
Basically had the main 655 handling all DNS, DHCP and gateway functions, the 655 upstairs only really used the switch and AP, all of the DHCP, DNS and other network stuff was disabled.
Replaced the main 655 with an 868 and am very happy with that. Thinking about doing the same for upstairs. Everyone says the 868 has better range than the 1525, so that is a concern. But when I had the 655 upstairs, even though nothing theoretically was routed and should have stayed on the switch, I had some weirdness that I attribute to it being a router (multicast issues with TiVo, etc.) So I thought that a 1525 would be the perfect answer, it gives me GB ports and an AP without all of the other stuff. The 868 is on sale at Frys this weekend, what are your thoughts on a second 868 vs. a 1525?