Byron,
I have a Denon 2807 and Aperion speakers, 533PT fronts, 533VAC center, and 632IC surrounds. I have used Audyssey MultEQxt when I dirst set up the system and have recently recalibrated after things got "broken in". The thing to remember about SPLs and equalization systems is that the equalization system does two things, the SPL one. With the SPL meter you can balance the sound level at a location. The Audyssey equalization does this as wekll. What it also does (and this is why I use it) is that it provides an analysis of frequency range information in the room (whats to high or too low) and creates an equalization curve that is applied to the outputs to the speakers. In other words, if your room is soaking up stuff around 1500hz, that range gets boosted. The idea is to creat as flat a frequency response curve as possible. The SPL meter hears total sound and can't do equalization by itself.
I have found that the Audyssey program improved the sound in my room, quite nicely. And since it samples at several points (not just one), you can in theory end up with a larger listening area, as opposed to a single spot where you use the SPL. You certainly can move around with the SPL and try to balance things at mutliple positions, but that's pretty hard. Again, I'm not an audiophile or engineer, but that's how I understand it.
Check out this link on the AVS forum for more info on Audyssey. It's a review of the automatic system on the 3806, which is pretty close to wwhat the 2807 has in it. You can also search AVS for Audyssey and get a lot more information about how it works.
http://www.audioholics.com/techtips/specsformats/AudysseyMultEQDenonAVR38062.php