I have the DA70 and (very recently) the FA77. I'd be hard pressed to recommend the FA77 over the DA70 given the price difference. From my experience I think the DA70 is the best lens of the DA limiteds. It took until I bought the FA31 to finally see a lens that had even better IQ than the DA70, and there's no shame in that as the FA31 is probably the best pentax lens of all.
The FA77 has a much bigger following than the DA70 though, and resale is probably better on that lens, and it is almost a stop faster. I have both and can't decide which one to keep
If you don't mind bulk, and aren't spooked by SDM, the DA*50-135 is a mighty fine zoom, Pentax hit a home run with the optical design of that lens.