Yup. Head nods everywhere.
Common consensus is that if you have Audyssey and a proper mike that came with it, at least use it to calibrate your speakers to equal levels. This will give you the best results to re-create the spacial audio effects as they were intended by the creator's of the film/music. There is a second phase where it corrects for your unique room characteristics across all the various frequencies, but that is another discussion.
In the absence of a receiver with an automated system, use an SPL meter to get them all as equal as possible.
After calibrating the levels to be equal, many people do in fact tweak the numbers just slightly. Especially the center channel. It's very common, to turn up the center channel a db or two in order to get more clarity in dialog, a track that often seems mixed a bit light in movies. If you have ever held on to the remote to play constantly play with the volume controls between dialog and action scenes, you know what I mean. This will rectify that problem without throwing the spacial effects off too much.
Finally, while Johnk is correct, Audyssey probably does do a much better job at calibration vs. the SPL meter, I simply can't resist my inner geek to break it out once and a while. Sorry John, but I do love gadgets, even when my brain tells me I don't need them.
