Distinctive ring for the Polcom 670's

All;

    I have over 100 Polycom 670's and I'm trying to get the phones setup such that the phones ring differently based on the caller or type of call. From what I've read, it seems to me that only phones that use the version 5 software such as the VVX phones support this feature. Is that correct? I know that there are other phone manufacturers out there (with much cheaper phones btw) that let you set the Alert-Info with a URL to a wav file. Any insight at all would be greatly appreciated.

Thanks;

Frank