**** I had this post all worked up, and then got distracted with work before it ever got sent. Probably pretty redundant at this point since I think it all got covered, but I'll send it along in case there are any tidbits to consider *****
Dirk, I ran the PSP2 with my Sony D50 quite a lot -- really a very nice sounding rig. I can dig up samples if you like. I did get together with a taper a year or more ago to do a controlled comp of the D50 line-in vs the M10 line-in (using the 2 outputs of a littlebox). We never got together though to swap files, so I've never heard the comp. I've heard that line-in the M10 is nice, and the D50 def has a nice line-in. A tad on the darker side, but not too much.
Another option, is to get the new Sound Devices USBPre 2 and run it behind the PSP2 into the MTII or optical into a D50. The USBPre 2 supposedly has the same A/D as the 722/744 and very similar analog preamps. So that would probably sound quite a bit like a PSP2> 722 combo at a lot less money. Potentially smaller too to run USBPre>MTII than a 722, though the overall size would probably depend on your battery solution. Certainly PSP2>USBPre will be smaller than PSP2>Minime, since the USBPre is really pretty small. If you really wanted smaller size on a particular outing you could skip the PSP2 entirely, otherwise keep it in the chain when you have room.
On the sound spectrum, I wouldn't put the PSP2 and V3 on the opposite end of the spectrum at all -- my ears anyway. The PSP2 is a transformer pre, but it has a much more transparent sound as a transformer pre -- much moreso than the SD MP2 or Neve Portico. And I think the PSP2 is much closer in sound to a V3 than a Minime -- to me the minime is further away on the scale from the V3 than the PSP2. But again, that's my ears.