All the aftermarket kits will probably be better than stock now that they've had ample time to develop around the 9R.
Presumably Burandt, Ibexx, Bikeman, SLP would all give you adjustable options and gains for $450-600 on a complete kit. But that doesn't answer your question on which kit to buy. It is worth asking yourself if you want to tinker and/or if adjustable weights are important to your zone changes or not.
I found the stock 9R clutching to be acceptable last season, and am at least going to start with stock again this year and see if it is similar and get a sense for whether the mapping has changed since the stock high elevation setup appears to be identical.
As most have said, ask your dealer or a good dealer in the zone you're intending to ride for a recommendation. Lots of options and most will probably be solid.
No matter what you run, keep those belts and sheaves very clean, and blow the dust out regularly. On the poos I replace primary springs every 400-500mi, and belts shortly thereafter. Always blows my mind when guys run dirty clutches, smoked belts and old springs and wonder why they aren't getting peak performance with all the other doo dads they've bolted on.