oh, i just started this so you will see everything from the FM transmitter to the daisy chaining of it all. For now, I am using cables...I used the FM several times, but I need a new antenna. Everytime I take it out, I come up with something new. Last time, I had the wind take my turntable arms for a run...couldn't mix...never seen it like that. Consequently, I have to make a wind-block for the dj stand...add that to the custom sub I am building for this...All of my boxes sound good, but I need a good sub for the low-end to make it all click. Not only does it fill in the sound, I can drop the bass on the boomboxes a bit which saves a bit of juice on the ni-mh batteries I use.
I am about 4 months into doing this 2x a month, but the rain here has killed me a bunch so this memorial day will be time #5 or 6. This thing is a bit like herding cats...it drives me crazy a bit, but you know that people just lose their minds when they see it...and more pictures get taken than I could have ever imagined.
My agenda for this event coming up is to get the the wind fixed...have good stable sound...and see how my new 975 with 400 watts RMS coming out of it via Car amps and car speakers. I use a deep cycle battery with convertor, but can get the 12v to power what I need, but it all adds up. So, far I am able to push this stuff for about 4 hours. That blows my mind. The best part is while the batteries for the boomboxes are 5$ a pop, they have 2x the amperage of alkaline batteries and can be recharged 1000x. If I use them 2-4x a month...you can see I will have batteries for a while.
Now you really want to get into the evil scientists mind, know this will all go solar soon. I can run a good solar panel into the battery generator and use the sun to power the gear and if cloudy it will pull juice from the battery.
It's quite a project, but at it's core I am using these boomboxes as a tool...so really while I am a collector, once this is done, i will sell them...but it will be a while. Moreover, so long as these boxes don't get stolen/broken or raped by a monkey, they are appreciating assets(i do accounting) which means if I buy right, I will make a little scratch on some of this.
BUT, all of this is trumped by the fact I am dj at heart and this is all about getting people together to hear mind-blowing music on a crazy sound system. This project is but one avenue to achieve this goal...
-L
Very cool man...you got all the big grails out there too! 
