I would actually evaluate switching away from using AFP with Windows servers. "Services for Macintosh" has not seen any work in a long time, and has some real issues, especially in the performance department. It is very much showing its age. I tend to aim for SMB as the protocol, but you then do have to deal with the usual issues (naming issues, and the hidden files that get created... not to mention that you have to make the transition all at one time, you can't reasonably use both at once).
You could also use Extreme-Z IP, but that is a bit costly.