If you simply listened to these various models in Best Buy, it was not a fair comparison as Best Buy does not implement the EQ program on their AVRs due to having to connect them to many different speakers in the room, otherwise, there would have likely been a noticeable difference between the XT32 used on the 818 and the 4520CI compared to only XT on the 7007. As far as the "professional calibration" is concerned, they use an Audyssey Pro Installers kit ($550+$150 license/AVR) which can be purchased by individual consumers (in fact a number of Denon 4311CI and 4520CI owners have purchased the kit to do their own professional calibrations). You would likely hear a 5-10% increase in audio quality so if $250 is worth it to you then go for it. You're much more likely to see the owners of XT32 models having the Pro kit calibration than XT owners due to not only the cost being less of a factor but generally a higher need for tweaking and optimization of audio fidelity. To BB's credit, that is a very reasonable price (if it also includes the $150 license for the AVR) as Pro installers will often charge closer to $400-$500 for that calibration.
Also note that for better audio fidelity, the improvement of using XT32 would likely be more significant than using XT+Pro Kit calibration, making the 4311CI at clearance sale priced < 7007 the better buy if the newer features (ie. 4K, Zone 2 (HDMI), gapless ALAC/FLAC, Spotify) on the 7007 are not required.
Edited by jdsmoothie - 11/11/12 at 3:29am