Okay, I finally got a chance to install some nice flat wound strings, and play with the setup a little on the new KPB5. This thing now sounds and feels unbelievable! The bad news is that my 75 P bass - itself a very nice instrument - is going to spend a lot of time in it's case because the KPB5 eats it both sonically and feel-wise. The 75 P will likely be on sale at a nearby talkbass website soon
A couple of things that may be of interest to those of you ordering AC basses...
I ordered a Dalbergia Negra neck on this KPB5. My thoughts were that if I was going to order a definitive P bass I might as well go all out, and that I should probably get the Brazilian while I still could. While there is a slight sonic difference to my ears, the biggest difference I find is in the feel of the neck. I'm not sure why that is, since technically I'm only supposed to be touching the strings, right? But there's no doubt that the DN neck is more responsive. My opinion only, and I may be losing my mind (two AC basses in 6 months is a good indication of that).
Also, I have the bent plate bridge. I was a bit concerned that the old style bridge would be a bit "fiddley" and hard to work with. It is a tiny bit fiddley, but it is not hard to set up properly and it really does sound good and authentic - definitely recommended, especially for the KPB basses.
I've been trying to spend an hour or two a day with the KPB5 since I got it last week, and am enjoying it greatly. The pickups and tone control are very good, a huge variety of sound but never too tinny at the top or too murky down low. Haven't had it out to play with people yet, but I suspect when that happens it will cause a bit of a stir, and I'm betting it will sit as solidly and organically in a mix as my RA5. These two instruments complement each other extremely well, and pretty much have a lock on all my musical needs. Of course, I supposed I could always get a fretless...