You should read the recent thread:
https://www.pentaxforums.com/forums/pentax-dslr-discussion/125094-k7-good-len...-kit-lens.html.
"Good glass is worth every penny".
If you feel that the 18-55mm will not fulfill your needs,
do not buy it, and invest in better glass.
Your decision will be motivated by your needs and your shooting. Unless you need the high-ISO, the K-7 is as good as the K-5 and half-price. Another alternative is the K-x. All these cameras are excellent bodies and you will not be disappionted.
The K-5 is the latest camera, and there are excellent users' reports. The K-7 is also an excellent camera with superb handling, viewfinder, WR and low ISO performances. The K-5 does as well but not better for all of these. Then why pay twice the price? The K-x is even cheaper with an excellent high ISO sensor, but it lacks the handling, viewfinder and WR.
I might be biaised, but I would recommend to consider the K-7 unless you intend to shoot with high-ISO. All K-7 users will tell you that the K-7 can perform very well in low light conditions, using different techniques:
- with some in-camera PP, it is possible to get very nice shots either with in-camera PP (see
K-7 High ISO Success!)
- with some dedicated noise reduction software like Noiseware and NoiseNinja;
- with some fast prime lens.
All in all, there is no point to get the latest camera body if you do not have good glass.