Which of any of these would be a good deal:
$400 for a CM9
$475 for MK9
$500 for PM9 (trying to talk down though)
Are any of these reasonable?
I would say they're all reasonable, especially for the MK9. I haven't seen one going for that low.
If it's all the same I'd try to get the CM9 to start and spend the extra money on mags and ammo.