I believe the rear shock on the Raptors is a decent unit. You might want to talk to a few shops that do rebuilds. GT Thunder resprung and revalved my YFZ rear, and it is a night and day difference. Plus I saved enough to put Float Evols on the front(there is a reason why you see those shocks on the front of a majority of pro racers machines

) My brother does run a Fox Podium X rear on his quad and it is pretty sweet. I don't have enough experience with Elka or Ohlins other than to say that you would likely be happy with any aftermarket shock if it is set up for your weight and riding style. I would shop around for a company that will rework the shock cheaply if you are not satisfied initially.