For a cheaper and just as effective an option - get some custom-made earplugs with filters built in. I got a pair of Specsavers with 25dB filters for £99 from their hearing centres - get a free audiogram from it too, you can get ones at a higher price with variable filters as well.
But I just wear a standard ANR headset on top (HNC-46 I think) and can hardly hear a thing, except the guy next door. This is on a 737 Classic and NG. Makes the walkaround easy too!