The other day maisenzasmalto posted photos of Essence Colour & Go Irreplaceable, and I thought it looked like it was crying out to be layered over something like China Glaze Channelesque. When I had some time for swatching over the weekend, I couldn't immediately put my hands on Channelesque; I admit I didn't try very hard once I found Below Deck, which is pretty much the same thing (see squared nails' comparison here). Irreplaceable was actually in the first place I looked, the taupe/tan/neutral shimmers section of my unswatched Helmer drawers.
I put two coats of Below Deck on all but my ring finger, which got three coats of Irreplaceable. I then topped the Below Deck digits with one coat of the Essence.
The shimmer in Irreplaceable is quite dense; close up it looks like mini flakies and there are a lot of them swimming around in the tan base.
As a layering polish, Irreplaceable is quite assertive; the tan base blended pretty well with Below Deck but it didn't fade into the background like the base of a lot of layering polishes will.
If you're looking for a warm glitzy neutral, Irreplaceable can fill that slot. If you're looking for a versatile gold layering polish, keep searching.