I have a ddm tuning kit I bought for my S. Great price and lifetime warranty. I was a little hesitant about putting a HID bulb in the stock housing but on the S model it works awesome. Very nice cut off line with little to no glare. I have the 35watt kit in 6000k. I bought the relay harness they sell as an option. It wires the ballast straight off the battery and uses one of the headlight plugs as a trigger. I didn't like how the lights would flick on when you turn the key to on and then shut off when you thumb the starter. It's really hard on the bulbs and ballasts. I did some research and ended up buying another relay and some wiring and made a second harness which triggers the ddm harness to fire the ballasts when the oil pressure light goes out. Works pretty slick. No lights until you release the starter. Hope that wasn't too confusing. It took a while to wrap my head around so it's kind of hard to explain haha. If you need anymore help let me know and I'll try my best.
DDM tuning has the best price kit I've seen. A lot of other SVRiders use DDM kits too. Just get the 35Watt H4 and whatever color you like (mine is 8000k). The whole kit is pretty much direct plugin, just need to find the space to mount the ballast (usually stick them behind the fairings).