Comments on the K3 mated with the Sigma 105 for macro;
This combination can produce some seriously sharp images, the APSc for macro is the largest size sensor I want to go with, you need to stop down to F8 minimum to get a decent depth of field and more often F11-13, at F16 the sharpness is already waning, FF would make DOF more of a struggle.
I find that the K3's sensor can take a lot of cropping so there is less juggling for DOF and closeness if you crop a little, unless you're looking for 20X30" prints! Image noise is your enemy when trying to freeze bees and the like I use 800 ISO for those critters (and in bright sunshine), I've lost too many shots trying to keep the ISO down, generally I start with with the ISO @ 800 and if I get the shot I'll try again at 400!
I know I was a late taker of the K3, so it's no news to those who have owned one for some time,however it is an enormous step up from the K5 and I'm using a 30% less sharpening boost to get significantly sharper images with less sharpening artifacts. I waited to for the mirror problem to get resolved in "vain" as I have had three machine gun attacks so far.