I agreee, in part with RMK2112, but need to clarify.
I'm not a fan of the Walker Evans Air Shocks for the 900's... especially as an aftermarket "upgrade"..
I am a huge fan however of the Walker Evans Coil spring Needle shocks... Compression adjustable, dual rate springs, large diameter shafts and excellent quality construction... Especially for the money. (about $625-650/pair)
Their are other shocks that are even higher quality like the Z-Broz or Fox EVOL-X...or even Ohlins (hard to get in the USA for the polaris mountian sleds).
The Ryde FX aluminum rebuildable shocks ON your sled now are top notch shocks... when valved correctly, I'd put them up against just about any other monotube/IFP shock. Definately better than the WE-Air shocks you are referring to.
T
OR.
Find someone that is upgrading their 2011 ProRMK front shocks and swap them out.