I have not personally tested these routers with IPv6 wireless.
I can offer this guidance:
This page lists routers that support IPv6 out of the box.
http://www.sixxs.net/wiki/RoutersIn addition dd-wrt firmware in the versions above micro and mini support IPv6.
Check that the router can be flashed with a higher version.
http://en.wikipedia.org/wiki/DD-WRT