Originally posted by clackers New, the DA35 and DA50 'plastic fantastics' work fine on my K-1, but the FA35 you may be able to find around that $300 range anyway.
The K85 f1.8 you might get around the $400 range, and you could sell it for similar to finally buy that FA77 - it'll be worth the wait!
Seconded, I have the DA35 on a K1 and it's great! The other 35s may be a tad better (I've never had one of them), but there's really not a lot of improvement to be made relatively especially for the cost!
(On a subjective scale, if a 18-55 is a '5' at 35mm, I'd say the da35 is a '9' and then some of the others may be a 10 but at triple+ the price, and heavier, but that's not a problem in this range I think).
If the K85 is over budget I'd suggest the M85F2 - "just" an M but one of the hardest ones to part with for me both becuase of iq, size, feel etc.
But if I dare mention zooms while at it, the Tamron 70-200 F2.8 is a stellar lens which can be found below $300 used, so that may fit the bill until you get the 77. It's large, but the smallest and lightest of the FF 70-200F2.8s, and great iq too for a bargain price.