Hi Sinbad!
On the topic of intercoms, as posted previously, don't scrimp on the cheap and cheerful ones you see on fleabay. Buy a well known brand, such as Autocom etc.. They have shot up massively in the last 3-4 years unfortunately.
It's worth the time also to really plan out the installation, both on the bike and in the helmet, as being 1/4" out with the earpieces can mean really bad results. Sometimes an MP3 player/ipod (which can be incorporated into intercom installations) will not like the vibration from a bike if you place it under the seat, and will stop playing.
If you are going to buy an intercom, I would reccomend chainspeed, as their after service and advice was superb.
Hope to have helped.
Kev