Race Tech and Hyperpro are both probably good.
I have a Race Tech spring set for the Valkyrie (not installed)... it is
more complex than just springs, so if you go that route, beware...
there's a bunch of shims and stuff you have to install correctly
or you'll probably just have a mess...
-Mike
Is that part of their Gold Valve kit? I had a neighbor who installed those on a couple of enduros. He said they were great. But installation was not easy at all. As I remember the washers are flexible and deflect if you hit a sharp bump to allow more fork oil to flow, essentially creating valves with variable sizes. He said he could ride over a rock or log off road and barely feel it. Sounds like an interesting system.