Hey I have a suggestion for you... do some experimentation before spending the big bucks on FF. From your current collection of lenses it seems like you tried to get a feel of Pentax without spending too much money. How about having the same approach to FF and if it works out, then go out and spend your heart out?
Get a Pentax film camera like the ZX5, ZX-M or Super Program that can control the aperture on your lenses, and a few rolls of Kodak Ektar or Portra. Get out with those 50s and the 35 and the 28 and shoot some scenes and some people. As you know, both DA lenses work on full frame as long as the camera can set the aperture for you. On the other lenses where you got the aperture ring, you're fine and could use an older mechanical camera like the K1000 or MX or Super ME.
After you get the films developed, see if the "full frame perspective" is all that it's hyped to be. If it is, get that Canon... as with all things digital, don't worry that the 6D is going to cost more in two months than it does now. Prices always go down, as the newest and hottest thing comes out
and there will always be deals on bundled lenses.
That's what I'm doing... the problem is, film is scratching my FF itch, and I see no need to invest a ton of money anymore, plus the film bug is quite contageous
and so far I've spent most of the time on cheap film... but it's so much fun...