Depends on the dealer, but many will transfer a P6.
It's a nice little gun. Some of the early ones have a hard time feeding anything but round nose FMJ, but you can get the feed ramp re-profiled to feed more modern ammo. It takes the same trigger parts as a typical P series so you can swap in an SRT trigger if that floats your boat.
This guy does the feed ramp work and makes custom P6 parts:
http://www.customizedcreationz.com/sigp6p225parts.html (Lame name but he does good work.)
Edited to add: The stock P6 mainspring is obnoxiously heavy. You can swap in a stock p225 spring for a lighter (but still perfectly reliable) trigger pull, or even go down to a lighter Wolf spring if you're willing to deal with the potential for occasional light primer strikes. (I think I put a 19 pound spring in mine but I don't carry it for self defense.)