As for pre/A/D... why not wait for the SD HD box? Pre>A/D>HD recorder all-in-one and it's the size of the USBPre...
As for mics, get some DPA's... your tapes will thank you
The MP-2 is definately stealthable; but you have to be pretty careful when crotching it, it bites
I don't think this has been mentioned, but the PSP-2 I just bought is the same size as the MP-2 and stepped-gain- set it and forget it!