The speakers probably aren't entirely run in yet, but they have at least 40 hours on them so they are far enough along to fairly comment on them I think.
First, let me say that I was a little concerned about the sensitivity rating of 86.5db with a 15W amp. I've had to go to school a bit to better understand what makes a speaker easy (or not) to drive. Turns out the Sierra's are very easy to drive, despite their relatively low sensitivity rating. Very few people would recommend speakers with that rating to a guy with a 15W tube amp. Well, the I84 drives these speakers very well. You can drive the speakers to pretty high volumes with no breakdown of the soundstage at all, nor any notable stress. I'm pretty darned impressed. I'm sure you could overdrive the amp, but I was able to get to levels above what I would ever listen to, so that's all I needed to accomplish.
The overall sound with this combination is very refined. Bass is goes deeper than any bookshelf I have ever heard, but it is nicely balanced and not the least out of place. The I84 controls it nicely. The midrange is smooth, detailed, and has nice depth. Treble is extended and not the least bit bright or fatiguing. I think time will smooth out the tiny bit of brittleness I detected. The overall tone of the combo is pretty neutral, perhaps a hair to the left, which is good as I enjoy a slightly rich overall presentation. I might even try to push it a little further that way through tube or cable changes.
Overall, I like the combination very much. I think you would be hard pressed to find a combination that sounds better for the $1600 (combined) I spent.
