I've been working on my install in my spare time. It's a 600w amp with speakers mounted next to my mirrors, the Sirius module on my handle bars, and I decided to put the antenna on the trunk. I decided to go with a truck antenna, all bike antennas had questionable(read: horrible) reviews.
This is the antenna I chose:
This is the radio mount I chose:
This is the sub/amp I chose:
I already had the sirius radio laying around.
I used some heavy duty speaker wire and a 40a relay from Advanced Auto Parts. Also some heat shield tape. I used a male to female 3.5mm wire at 6' length to attach to the 3.5mm jack out of the amp, then put another male to male 3.5mm out the back into my saddle bags along with the volume control. My only complaint is the volume is VERY touchy, and the volume control wire is really short, with no real way to extend it. However it's threaded so I may drill a hole in my side cover and poke it through, then put a nut on it, so I can just reach down and crank the volume as needed.
In testing, the speakers get way louder than necessary. Only about 1/4 volume and they're almost to loud to stand next to.
Here's the picture of the install of the amp under the seat. I took a license plate and some metal sheers, and cut a piece with a tab off the side that I folded down, that slips between the battery and metal piece to hold it in place, then the rest of it just sits perfectly.
Here's the antenna. I went with the back instead of the handlebar. I'm not sure how I feel about it, but I'm not sure of a better place. Maybe I'll put some flags on to make it not stand out so much.
Here's the radio and the speakers. Iphone mount will go on the left side.
If anyone has ideas or feedback I'd love to hear it.