On a '15-16 truck the Elite kit will be more expensive, compared to going with the 6670. All the parts are not apples to apples though. Our accessory parts are better materials than the oe pieces.
On an '11-14 truck the cost is pretty much equal between the two and as mentioned above, our parts are better material than the OE retrofit.
As far as whistle, ours sounds like an '03 6.0L.
I would love to see a dyno comparison of the 68 vs the 66, we will see how the future plays out on that.
On a Dmax the 68 has made 825hp.