I swapped my stock suspension for an extra 12...a world of difference, I mean, night and day as said above...I've heard good things about the xtra-10 also, but I prefer the comfort of the 12 for the trails I ride.
I'm not a really aggresive rider, but love deep powder...I have never bottomed out, ever...not a hard install, and absolutely worth the money and time...
If you want some pics, take a look here..
http://www.misdirection.ca/index.php?pr=My_Polaris_Indy_XLTthats my site (hopefully I'm not breaking any advertising rules)
If you need more info...Ill be glad to help!