My AVR doesn't have any of the fancy-pants auto calibration stuff, so I'm stuck in the stone-age and have to use an SPL meter. That said, I have read of others complaining that the auto calibration routines sometimes don't work very well. YMMV.
My opinion, FWIW, is that before I spent $3,000 on new equipment, I'd spend $30 on the radio shack SPL meter and double check the calibration. If the calibration is spot-on, and you feel the SPL meter unnecessary you can always return it.
Actually, I use my SPL meter for all sorts of fun things, like making sure I'm not overdoing it on the volume level, or testing how loud my motorcycle is, or seeing how loud my buddies can burp...
