Hmmmmmmm...

The Shiva has dual 8 ohm VCs, so parallel wiring makes it a 4 ohm load.

The 7100 is rated at 165 watts @ 4 ohms.

Sensitivity of the Shiva is 87 dB, 1W/1M.

I doubt you'll get ref level bass with this combination.
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The thing is, I don't think I'm getting the output I should from it. When calibrating my speakers using the internal test tone, all of my speakers calibrate to 75db at -9db, give or take.
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What is the main volume set at when you calibrate?

How big is the room?

What source are you playing?

Is the amp distorting when you 'crank it to +10'?

Also, you have no phase adjustment with this setup, and This may have something to do with the apparent anemia. Try reversing the speaker wires to see if there is any volume difference. Use your SPL meter and play a bassful tune, switch the speaker wires, play the same passage and note the SPL reading.