It's me again...
From what I have seen in terms of quality of images (and also financially), it might not be really worth it to swap KAF-8300 for a 50% smaller ICX-814. For narrowband imaging, I would not stick ICX-814 on any scope above 600mm FL, with 400-500mm FL being ideal for this sensor in terms of FOV and image scale (arcseconds per pixel). Maybe it would pay off to wait a bit and see how CMOS sensors evolve over the next year or two
I feel that Sony will eventually come up with some very nice CMOS sensors suited for astrophotography, with very low read noise, good QE and a decent size chip.