RE: SS
I used FlightCom equipment. So far I am really impressed. I use it for driver-passenger communication when I'm on the freeway (it's pretty loud in there) and I use it daily to listen to my MP3 player, too.
The main unit is a FlightCom iNova, and my headsets are 4DLX models. I bought all of it off of Ebay. The iNova unit is discontinued, but it is almost the same as the the IIxs model (the only difference is the iNova is stereo, the IIxs is mono).
The really cool thing about it is that it offers full-duplex conversation. There are no push-to-talk buttons, no waiting for your turn BS. Just talk as normal. It is voice activated, and it trips very easily, so you don't need to alter your voice to activate it. When you are done speaking, any audio you have piped it through the Aux input comes back on. In my case I have MP3 player feeding tunes into all the time. The audio quality is surprisingly good. Not much bass obviously, but I listen to rock music on it and it sounds good.
If you buy the headets off Ebay make sure you don't get headsets with the helicopter style plug - it won't fit the control box without a $35 adapter (each headset). Also, Don't make the mistake of buying a headset without a microphone. They are about $50 each... I've got two headsets in the boxes I bought and cant' use because they are heli style, and one is missing the mic.
Here's a picture of how I mounted my setup. The whole system is made to run off a 9 volt battery, but it also comes with a 9-32 volt power jack, so I wired it to a toggle switch on my dash, and fed power from a 12v fusebox under my glovebox. Otherwise the only way to turn the power off is to unplug the headset plugs. This way I just flip the switch and I'm on. Even got a red indicator light. The other wire is the aux-input patch cord. It's what you use to plug an MP3 player into a car radio. $3 on Ebay.