In the Setup Menu of the AVM 20; under Speaker LVL Calibration, all speakers are set at 0.0 dB. Is this the norm?
No - with all speakers set to 0dB, that suggests the system has not been calibrated.
Should I be adjusting the Front 2 output to match the Center output? Is this the purpose of the Speaker Lvl Calbriation Menu?
You need to get a sound meter (either a Radio Shack meter for about $40 or $50, or an iPhone app for a few bucks) and use the AVM20's internal test tones to adjust
all of your speakers (fronts, center, surrounds, and sub) individually to achieve the proper output. It is likely that each speaker will have a unique setting, as the calibration adjusts for speaker efficiency, amp gain, and room gain. The AVM20's manual should have some instructions for doing this with its internal test tones.
Also, you should check to see if the distances have been adjusted.