I went with the Baron 8523RD spring on a stock TW2000 shock.
As far as I can tell it's the same as the heavy Pro-Cycle spring, but half the price ($70 shipped on ebay).
I used Pro-Cycle's hydraulic press method to compress the spring, and it was pretty easy.
I'm 260lbs, but I do not ride aggressively. This spring (along with Pro-Cycles heavy duty front springs) makes my TW feel just right to me.