With the disclaimer that sound is very much a personal preference I'm of the opinion the K&K does sound very good as a passive PU, but the addition of a pre-amp will improve it. I've installed over a dozen of these in various guitars. Dreads, OM's, 6 and 12 strings. Parlors, even a uke. My personal favorite from K&K is the system that has a small onboard pre-amp, a volume control and a phase switch. I've also used guitars with just the passive Mini. Many do not like the idea of a battery inside the guitar. I get that, so a outboard pre-amp makes perfect sense. It's not just a volume issue. The signal coming from the guitar is not just hotter with a pre-amp, but to my ears has more clarity and presence. So the guitar sounds fuller even at lower volume levels. I'll also add I've run various guitars with the K&K thru a bunch of different PA's and amps. Passive speakers, powered speakers, various mixers, stick systems a'la Bose or Fishman. The K&K with the pre-amp has always sounded good.