Check out accessories4less. They have 8805 and 7705 refurbished units with 3 year warranties at great prices. If you search, you'll find a thread somewhere where a group got together and compared the sound quality of one of the 8800 series processors with one of the 7700 series (sorry, I don't remember the exact model off the top of my head) and found no noticeable difference.
When I bought my 4K TV and decided to upgrade my processor, I went from the 8801 to the 7704 and have been very happy with it.
Unless the 8805 has some connectivity options you need that the 7705 doesn't have, I'd give serious consideration to the 7705. In my system, the 7704 is as good as, if not better than the 8801 was and considerably cheaper.
When I bought my 4K TV and decided to upgrade my processor, I went from the 8801 to the 7704 and have been very happy with it.
Unless the 8805 has some connectivity options you need that the 7705 doesn't have, I'd give serious consideration to the 7705. In my system, the 7704 is as good as, if not better than the 8801 was and considerably cheaper.