I've tested the HD-P2 against my EgoSys WaveTerminal 2496 soundcard. both are bit-perfect.
If you're always planning to run the V3 (or any other external A/D), I think the 722 is overboard, and you are best off with the 671 or HD-P2.
I went with the HD-P2 because it is not picky about 8 gig CF cards. (I know there were issues with the 671 and 8 gig cards. If these issues have been resolved, then this issue is moot. but I haven't heard positive reports yet.)