If you are interested in one of the longer lenses, there are 2 separate 2 lens Kx kits available from Pentax - one including the 50-200 and the other with the 55-300 lens. The 55-300 lens is much better than the 50-200. The 2 lens kit is substantially cheaper than buying a single lens kit and then looking for the second lens used.
Now the only slight difference is that in the kit the 55-300 comes as a DAL version, which has a plastic mount, no focus clutch nor lens hood, otherwise its optically exactly the same. Personally, I would just go for the DAL version and not worry about the differences.
For the 2 lens kit with the 55-300 its been noted that its about $140 more than the single lens kit. The DA 55-300 sells new retail for about $420. You would really need to look around for single DAL 55-300 but I think I remember someone posting that they were going for about $200 by themselves.
So in terms of value for your money, purchasing a 2 lens kit is the best bang for the buck.