A topic that has been discussed here many times. Here is the link to the product that Evan is thinking about. They have been around for a while, but I can't remember any posting from a member who has tried this.
I can tell you that IMHO the BL3500 is completely inadequate as a center speaker, even with an AV7000. Again, it's just my opinion as a current BL3500 this is not the right speaker for the job. I love it as a link speaker, I think that the design is teriffic, and from a sound point of view adequate as a link.
I also owned an AV7000 (once upon a time) and I would think that it's propbably not worth investing a lot in keeping it alive. Might I suggest a descent pair of passive speakers for your center channel project?
BTW, Cary CD player... Wow.