I like Pro Ears for hearing protection, I have a set of their passive muffs that I use along with soft ear plugs. In general the passive muffs will have a higher noise attenuation rating than active muffs, and it appears that you need the highest attenuation that you can find for your .454. Typically the maximum attenuation that you can find is a noise reduction rating (NRR) of 29 or 30. These are large muffs, which may not work well for rifle work, but work well for pistol use. Here is a link to the Pro Ears comparison
table, they list a couple of models as best for indoor pistol use.
Don't discount the use of plugs under a set of muffs; the plugs add some attenuation above what you get with the muffs and can make up for a less than ideal seal around your ears due to the wear of safety glasses. Try a few different brands of soft plugs to see if there is one that you find comfortable.