The Pit Bull, Scotts and GPR Damper are all pretty similar in design and seem to get nice reviews, I have a Matris M3 and really like it.
http://www.matrisdampers.com/
I would not recommend lowering the rear suspension, all the people I have talked to who have attempted this reported poor handling to be the result. You are correct in that the geometry of the bike is what helps it handle so well. The best mod I have made to my bike in terms of suspension at this point (I still have all stock suspension components until sometime this winter) was to loosen up the forks in the triple trees and pull them down until the very top of the fork caps was even with the top of the top triple tree. Of course it goes without saying that you will then want to tighten them back up in the triple trees...
The 675 from the factory is set with about 4mm of the anodized fork tube sticking up above the top of the top triple tree. With it set this way, the bike is very flickable. However, the front end suffers from a little bit of a vague feel under hard cornering (like on the track) and has a tendancy to tuck the front end with little warning. By lowering the forks in the triple tree you are effectively giving the bike a little more trail in the steering geometry, thus slowing down the steering a tiny bit. This gives the front of the bike more feedback to the rider and less likely to tuck without warning. It remains very flickable, just picks up some predictability.
Congrats on the new purchase and welcome to the fray!
TripleThreat
