Hello and welcome to the forums.
Originally posted by semaca "who buys a Pentax? That's crazy!"
That's pretty much the exact words my sister used. And then she did some research, after which she just said "ah".
The K3 is something to look into. But, as savoche wrote, you should think about why you want to move brands. It is a tough choice to make.
I got the 18-135mm as kit to my K3 and it is a really lovely piece of glass to start with. If it fits your budget.
There's a good review about it on PF.