Both are great options and both impressive. I got interested in horns when I heard Khorns and have a set of Pi 7's now.If you like the characteristics of the Khorn sound (almost physical feeling while listening to sound, clear and effortless) you will like the Pi 7's as well.
There are many options that do this and you get to see them at get togethers like the Mid West Audio Fest. (might be a shameless plug for the April 2006 get together )
Grant.