If you don't make big prints, only view the photos on screens or web (like most of us do nowadays), I don't think you'd see much difference in IQ between an APSC or FF sensor unless pixel peeping.
And I agree bigger sensor doesn't mean better image. It's not the camera which makes the photo, but the photographer
Still one cannot help but imagine, a FF with iso capability of the K5. Personally for me since i work in stadium or worse lighting, it would be amazing.
By the way, any idea when a "Preview" review of the K-30 will be coming out. Since most likely using pre-production firmware and sensor, i wont ask how the pics are but can anyone demo the shutter noise or the buffer with an Extreme Pro Sandisk card to see how many jpegs it can fire at max resolution in or is the buffer large and quick enough for undisturbed shooting all the way till card full? Can the camera AF track subject movement quickly and importantly can it lock on dark or close to black subjects?