Looks like Great Plains Audio has finally come out with the new 604 they had told me they were working on.
http://www.greatplainsaudio.com/two_way.html
From the pictures, it reminds me quite a bit of the original Urei (before the shadow slots and foam treatment).
DIYers looking to build Urei replicas should be grinning ear to ear with this new model, I'm quite excited to see this in production!