Was gonna ask if NRRs are truly additive, but found this info:
When hearing protectors are worn in combination (i.e. earplugs AND earmuffs), rather than adding the two NRR numbers together, you simply add five more decibels of protection to the device with the higher NRR. For example, using 3M E-A-R Classic Earplugs (NRR 29) with 3M Peltor H7 Deluxe Earmuffs (NRR 27) would provide a Noise Reduction Rating of approximately 34 decibels.
So plugs and this would give me a NRR of 39 dB NRR.
My current setup is 33dB NRR plugs + either 23dB NRR Howard Leights or Walker RAs, so I guess I'll stick with what I have. May just pick these up just as lenders.