I changed the stock pup in my J-45 (a fishman matrix back in 2005) to a k&k mini. This was better than the stock pup, but I was never really happy with it. Ended up installing a L.R. Baggs M 1 active. I really like this one, much better than the stock and better than the k&K, at least to my ears. I guess there are better pickup options out there, but these are way more expensive. I think the m 1 looks cool too, and you can remove it, when you don't use it.