Is $650 for a used P320 x carry with box, unknown round count a good deal or not? Overall condition of the firearm is good to very good.

Look over these and factor in your FFL transfer fee and see for yourself.

http://www.sigsauerguns.com/fi...l?dir=asc&order=name

That is way too high. New ones are selling for $659.00 and used ones even less. There are several on Gunbroker for the $659.00. Of course like Berg said, you have to factor in shipping and ffl costs. Even still, for only $40-50.00 more, it would be worth going new.

Do you want a warranty?

Used SIG - no.
New SIG - yes.