The 40 is a 26/27 on full frame and will set you back about $4000. The 32HR is the gold standard in that arena right now (about a 20 on FF), and it will set you back about $8,000. The 35 is a 22 equivalent for full-frame MF, but they are older designs -- not bad, just older and so have more falloff. In 35's, the SK is the one I would pick, but as mentioned earlier, you'll want to add the Center Filter and leave it on for most shots. You can probably find a used one for under $3,000, but add $400 or so for the CF.
If you go with a crop sensor, then you need to look at a SK 28 for your 24 equivalent. The downside is a really small IC so not much movement (a little on the crop sensor). But mostly that if you ever upgrade your back (and you will) it will just barely cover full-frame, and has heavy lens cast even on the P65+/IQ160, and so much cast on the IQ180 it won't correct.
The 28 is the current "no man's land" of tech lenses. Many of us (ME) really want a good 28 solution and there simply isn't one. The 32 HR is a phenomenal lens, but not quite wide enough for my needs. It appears I am going to have to settle for going more wide than I really want and get the 23, OR do what I do now and save $8 grand by stitching the 40...