My take on 5Dc vs 60D is this:
5Dc does nicer images - I put this down in part to the noise being much more pleasing, more like grain than noise (although there doesn't appear to be an auto ISO option (should you wish to use that) - someone please correct me if I'm wrong on that), where as on the 60D I just don't like noise there at all.
Also the interface and screen are very basic - you will notice a BIG difference there, its a huge step back in technology, but oddly not as much of an issue once you get used to it - also no live view, which can come in handy for manual focusing - more so if you're running Magic Lantern's visual focusing aids on your 60D.
Full frame by itself brings complications, firstly everything will seem further away and you'll have to think more at first about which lens to go for, also and most importantly a load of your lenses may not be usable due to stupidly high vignetting, because they were not designed for FF, it looks like you'll be okay with the 50mm and 85, but if I recall Sigma's DC is for crop only
, so that would have to go.
I also see you do video, the 5Dc doesn't have that feature - that came along with the MkII.
My advice would be keep the 60D for video and things where you need the speed and reach and get a 5Dc cheaply - I was lucky and found mine for £505, so there are bargains to be had. Also that will mean that you not only do you have a second body but also essentially have more lenses too, in that the 50 & 85 will sort of act like different lengths if that made sense.
Oh one last thing that no-one mentions, if you;re running Windows 7 64bit there are no drivers, so while you can switch it to Print mode to get the images off the camera you cannot tether it without jumping through all sorts of XP compatibility options - which is only available in Pro/Ultimate, so not on Home - very annoying indeed is a modern(ish) product.