I read your post and some of the replies....
I have to agree with folks that are suggesting to FIRST look into your post processing. Take on a differnet approach to it. Also I think you underestimate the "negative" impact the AA has. I am surprised you didn't get a D800E?
(I know the moire). I don't do a lot of fabric, and willing to do the post if I come across the issue. for 10 years it has happened a hand full of times that I was easily able to manage.
Years back,before I purchased a DB, I had a 1Ds and I also had a Kodak SLRc. The Kodak had no AA, and the files were 3D MF like. The 1Ds was soft. (The "bite" has a lot to do with the AA)... Except I had such trouble with the way the Kodak handled lighting, specially if any came in direction of the lens, I would get magenta overcasts and such, so I put that down and went the MF route. Shame about the Kodak, it had a great software tool set, ISO 06!. I would guess the same sensor was what made the Kodak Db so successful for a while.
I have been meaning to rent a D800E to see how it would do with my studio shoots. I would never consider a camera with a AA filter for my studio needs.
I also think the way lighting is setup gives a great impression on the overall impact of an image. I have seen well balanced light from a 35mm look very MF tonally. Before you plunk down any money, I would do as others have suggested and see what you can do about exposing in the lighting, and post processing. (Sometimes slight fill lights can do wonders in giving you range).
The problem with the above info I give is that I have only compared a P25MFdB to my AA-soft 5Dm2 as a equal mpixel size. The Kodak was 14mp, and the 1Ds was 11mp. So if the NonAA D800E is anything like a Kodak SLRc at a 36mp resolution, this SHOULD bypass a P25 MFdB
There is a 2 bit difference between most top end Dslr vs MFdb, 14/16 bit, 2 channels are for noise... Erik had written something about it a while back.
I have been using this back for some time, and I do love the results. I do want more resolution and more DOF, so that was my reason to look for the D800E. But I don't see myself doing anything about it.
I do rememebr sopmething about the P30 that I would avoid. Something about the lens over sensor aliagnment, is not suited for Tilt/Shift if you ever do go toward tech cam.
Also, I LOVED this on the Mamiya RZ. I have a 35mm lens which is a bit fishy, but an amazing lens. The glass is really good, and overall a great setup. Beautiful large view(I switch the gg glass to brighter). I would also caution about the Hass software RAW converter, If C1 has support for Hass, then no prob. But I had bad experience with it when testing years back(surely they must have improved). I think the P40 is a top contender also for long exposure, and the 45 all around. I was looking to upgrade to the P45, and see them online for about $7-9k. If I had a great gig and justify it I would get one of these.
Sometime back, the MFDB makers were adamant about the photosite size being the dominant trait compared to 35mm sensors(reason the 1Ds files are beautiful /11microns), as some are 12microns large. Now with newer MFDBs having 6 or so, and surely technology has gotten better with less gap microlenses, better SN ratio, light fill factor, etc... did this bridge the gap? and if so, why couldn't 35MM with the same range photosites be on par with the MFDBs? Maybe if Foveon would license the sensor there maybe some interesting designs in the future?
I hope this helps.