Hi Don, been a bit busy recently, but have been looking in frequently to keep up with things in this thread. TBH I'm a little confused as to where you are at with all this business, though the overiding impression I get is that you are still striving for perfection, going to great lengths to prove the definitive method to achieve it.
My personal feeling is that all this business of 16 bit Tiffs is a little OTT. Onscreen at normal viewing of an image it is totally unnecessary, and you cannot tell the difference. You have infact been to great lengths to prove this in your examples, I was gobsmacked with that
Even for print purposes I have never seen any advantage. Not only this but the 16bit files use in PS is limited as many of the commands are greyed out.
As for this latest post showing the photo from the 5400, I really can't see the value in photographing an inkjet print then enlarging it to the extreme, what value does it serve? Have you not still got the original file you could compare with one from your D100, that would certainly be more interesting for me.
I have today been printing some images taken earlier in the week on a Canon 20D (8.2MP). They were adjusted to suit in ACR to a jpeg in PS then tweaked as necessary, though this was often just a case of straightening verticals etc. They were printed using the Adobe RGB colour space on my Epson 2100 to full A4 edge to edge. Frankly I would defy you to tell the difference between them and a MF print, and the colours etc are better than most I ever got with film from my pro lab.
Good to hear the news about getting the thumbs up on a new PC. Consider at least a 3Ghz AMD or P4 machine, with a 256mb graphics card and 1GB+ of Ram. At least a 100GB HD would be good. At least 4 USB2 ports and a DVD rewriter. Forget a floppy drive, not even sure they include them these days. Bet you have it all planned already
Pity about the software though, suppose it was pushing it a bit
Have you considered PS Elements 4, it contains ACR and of course uses similar or same protocols to the full PS. It does lack the Curves tool though there are ways round that. Much better bet IMO than PSP6