Originally posted by ZizZ^ Stay with Nikon. You are invested in one of the best brands for DSLR's with a much greater availability then Pentax and a much wider selection of lenses and gear.
you can get a D7000 for 900Dollars right now wich is just a bit over the K30 price and is arguably still the best APS-C dslr out there ...
You ll loose morey money if you have to restart a whole new system imo.
I wouldn't really describe the OP's lens list as being "invested" in Nikon. I think you could get the K30 with 18-135 in a package for 900-ish which is what your D7000 body would cost alone. With any money left over, look at the Pentax DA 35 f2.4 or Sigma 30mm f1.4 and you are set with the same type set up.
I really think the big question is if there are other lenses that the opening poster is interested in down the road. If so, that needs to be a factor. I feel like for most lenses, Pentax has a decent selection. Currently there is no full frame option for Pentax, so if that is a concern, than definitely stick with Nikon. Also, If super-telephoto (longer than 300mm is needed) than Nikon definitely offers more options. At the same time, I believe the K30 body matches up well against the D7000 body and the K5 II actually surpasses it.