We have about 7 or 8 Macs on our network as well, and out of all the products that we tested we found that http://www.thursby.com/products/admitmac-eval.html to be the best solution for our needs.
It allows you to join Macs to AD and somewhat resemble behavior that of a pc on the Macs, it even allows for some scripting for logon mounts, printers, etc.
Windows share (cifs/smb) permissions are respected for the most part unless you have funky settings traversing different directories, but I would do some testing before implementing, since SANs tend to behave different.
Let me know if you want me to send you more info on how we do things here.
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