Dear evgeny,
Although I think the P30 or P25 wor even P21 would be no question relative to Kodak back, I would caution against running to a D3 or other 35mm system. Even old MF technology had a better IQ, to my eyes. I reviewed some of my older Kodak back Contax 645 images, and am still impressed, sometimes they have a real filmlike quality, and the 'looks' software for Photodesk created some wonderful results.
Here is an example, outake from a travel series, that was is poor light but still has wonderful depthg. The 100% crop has jpg artifacts but raw is clean.
I would suggest getting some raw images to play with.
I would be happy to send you some .dcr files, and Photodesk from Kodak is free.
regards
Victor
PS: I did trade up to phase, so I no longfer have. But even for $5k I would get the Kodak back again instead of the D3.