Anders,
I would get the P30. The P30 is a more flexible solution than the A22, if for no other reason than ISO. The Phase is OK at 800, and I've heard the plus is OK at 1600. The Aptus backs need light and lots of it to shine, although I've seen some A75 files at 400 that looked pretty good. And I do agree that the Aptus backs provide great results out of the box for people, but you can get the same results with Phase backs, you just have to have your presets in order in whatever raw converter you use.
Also remember that the Aptus is the same generation tech as the ZD, although it has a better pipeline. I'd get the newest tech you can find that fits your budget.
After all of my bitching about MFDB prices and my evangelizing for rentals, I pulled the trigger on a P30+. I usually rent Aptus backs for jobs, at least since LC11 came out. I really like the A22 and I think the A75 is the best back available, but they cost too much. The A22 is old tech, and now that the Hallmark refurbs are all sold, the prices are back in the $13,500 - $15,500 range, which is just stupid. A75 prices for refurbs are generally in the $16,000 - 17,500 range, which is better but too high for my Scottish heart to bear for last generation tech. The A22 needs too much light, in my opinion, and therefore requires strobes or at least bright, bright sun. ISO 160 seems to be the max for client usable files. In my experience shooting beauty, the P30 has clean files to 400, 800 in a pinch. I ended up getting a new P30+ (Thanks Lance at Capture Integration!) for what was a very good deal. While I've never shot the + back, I am told 1600 is usable if need be. I'll find out when the + arrives. I also find the Phase backs very reliable. The whole package just works and works and is simple, its usable in low light, and you can use a higher ISO to get better hand held shutter speeds in natural/ambient light.
In looking at your list I think the Phase hits all of your requirements. You may also look into a used H3D. I retouched a bunch of H3D files for a friend last week and wow, really nice files and clean at 400. The files out of Flex have a certain lightness to them, the colors seem delicate and very smooth, almost like a pastel. The lens correction in Flex is real. It really is nice. Used H3d-22 with the H3 and 80mm runs about $13,500 - $14,000. Lenses are expensive.
I also like Sinar backs and have used the 54m when it first came out. Fantastic quality. But Sinar's presence in the US is strange. The best resource Sinar-Bron has in the US is Thierry on this board. Thierry, a Swiss expat Sinar employee stationed in SE Asia is the best source of info for potential US buyers? Isn't Sinar USA in Jersey? Or I could deal with the Fotocare, which sucks.
Good luck with this process. Its worse than buying a house or car.
