4yanx,
I have the 5As, and have set them up personnally along with a number of other similar hi end 5 or 5A systems in the area. In doing so, I have used a number of approaches including the RS meter, a Behringer RTA, and laptop SW called "Room EQ Wizard".
First, in my opinion, these speakers offer tremendous performance if set up properly. They can be totally coherent across the 4 drivers such that you can not hear the speakers, and you can not hear any cross over effect between the drivers, including the subs. I believe you would be doing yourself a great disservice if you tried to do this by ear.
That being said, I don't know what penchant you might have for aquiring the equipment and knowledge to do it yourself versus getting a professional to do it.
Currently Richard Vandersteen is recommending a procedure for how to do it with a RS meter in the instructions that go with the Quatros, and it would apply equally to the 5As. It is very straight forward, and if your room is not particularly problematic, it could get you quite an acceptable solution. However, I have found that real additional improvements can be made with either the RTA or Room EQ.
The RTA provides real time measurement in typically 1/3 octave bands and you can adjust each sub while playing pink noise while looking at the display. It is best to use an RTA plus a good quality calibrated microphone (total about $350). However, the nature of pink noise is such that the amplitudes of all bands are continually varying, make any precise setting an averaging at best.
Room EQ is shareware SW running on a PC augmented by a USB external sound card driven by a RS meter as the microphone. This combination is only a little more expensive than the RS meter alone ($50 for the sound card assuming you have a laptop). It works by calibrating the sound card and microphone and then sending a sweep into the room and capturing the response. A measurement can be taken in a couple of seconds and saved as a plot to the disk (unlike most RTAs). This method is very precise and very repeatable, and is capable of showing the difference in response when moving a speaker by as little as 1". It also reveals those very narrow peaks or dropouts that an RTA cannot see. There are other similar SW products that will do this as well, such as ETF version 5 etc.
I have gone into rooms where dealers have "set up" 5s and made noticable improvements with the Room EQ approach. It is very obvious to me that getting the bass right affects the mids positively every time. I have shown graphs of this approach (before and after) to Richard and hope to have more dialogue on this with him during the upcoming HE 2006 in LA.
I hope this is helpful and not discouraging. A little patience and extra effort here is well worth while. Let me know if I can be of further help.