The Biketronics RetroRadio kit I purchased for my '08 FLHT included a Sony CDX-M50iP Marine head unit, Biketronics controller, and a pair of Hogtunes speakers. This kit cost me $520 including shipping. If you choose a more basic head unit, you can actually put together a kit that will cost you under $500. Of course, as already shown, you can spend as much or as little as you want (or need).
Because I chose a Sony head unit to go with my Biketronics kit, all the handlebar stereo controls function including AVC (automatic volume control), a feature I consider essential on relatively loud motorcycles like ours. I set the volume to a nice, acceptable volume at idle and forget it. When I get into the throttle, the stereo's volume keeps up with the engine/exhaust noise.
These systems look and sound great. I'm only pushing two speakers on my FLHT which might be the difference, but my system sounds great even without the addition of an amp. I can't imagine what the sound quality would be like if I added one, but it must be thrilling for those using one.
