Congrats on getting the custom plugs! I got mine just a few weeks ago and I'm so happy I did! To those on the fence, they really don't mess with the mix much at all, just straight volume cut. Mine ended up costing me around $220 Canadian, so they are a little pricey, but to save my hearing in the long run I think it's worth it.
Anyway, to get to the original question, I have 15 dB filters in mine and I think they're perfect. My band used to jam ****ing LOUD, and I still wouldn't go higher. 25 dB cut would be too much for the "not so loud but still loud" jamming situation, and 15 has been perfect for anything I've thrown at them so far.