Where do you have your receiver placed that you can only reach two seating positions? The advantage of Audyssey is that it can optimize for multiple seating positions. I found it very good for setting trim levels and speaker distances.
With the radio shack meter, you set it on C weighting and play test tones through your speakers. The receiver should have a pink noise (a wide band of frequencies) generator that sends the same signal through alternating speakers on a set pattern so that you can compare the sound level of each.
A tripod is handy for holding the meter steady.
The receiver is 40' across the house in a rack. The Audyssey Guy (AVS) says you shouldn't use extension cables ("rolls offf the highs"), But to reach the main seating position I have to use the mic cord and a 25' extension cable. The room is small and 95% of the time there are only 1 or 2 listeners sitting next to each other. THe 3rd position is a little off center for the display, but totally viewable. But not used that much.
