I have two HC600's and one RC60 (the older model). Obviously I love them and think they are well worth the extra $$'s. Having gone through 4 other models only to have missed photos, I wish I would have had one of my older trail cams to set up side by side with a Reconyx to see how many missed photos there might be.
On my first Reconyx (the RC60), I bought one of the Reconyx security boxes and although it might be better than nothing at all, it is really a pretty cheesy security box in my opinion and difficult to slide open as well. When I bought my first HC600 Reconyx, I shopped for a different brand of security box and found a guy on Ebay that makes them. They are MUCH better than the Reconyx security boxes. Here is his Ebay site for a listing he has right now.
http://www.ebay.com/itm/Trail-Camera...item20cbd8d425 His Seller name is "custom1enterprises". I have looked at his other Ebay items for sale and it looks like he also makes security boxes for other trail cameras as well. I only have experience with the Reconyx compatible boxes though so I can't speak for the other boxes. I can say that the box is an exact fit and is set up for 2 Python cables and a door lock. They are a much heavier steel construction with a powder coating that is still like new after 3 years I think it is. He also sells the locks on Ebay all keyed the same, but I found them on the internet a little cheaper and all keyed the same as well. Just an FYI.