I have been driving on HID conversions for the last 10 or so years and have tried most things that have come to market and here is just one person's observations and opinion about HID's:
1) Don't use HID's in a reflector housing only in projector housings, the Genesis uses projector housings so conversion is a great idea.
2) Don't cheap out on headlights, a good set of HID's will probably cost $120-$200. If you buy cheap you will be regretting it from the first time the flicker starts, a ballast goes out, a bulb burns out etc.
3) Get a color temp of 4300K to 5000K. 4300K is the color of most standard OEM HID's, 5300K is a little whiter but not blue. Anything over 5000K will have a blue color and may look OK on dry pavement with good line markings but as soon as it rains you 'll be asking how come I can't see the road.
4) Buy the 35w version, you won't really be able to tell the difference between 35W and 55w. The 55w units have been known to deform headlight buckets from heat, degrade quickly and are prone to half the life of 35w bulbs and ballasts.
4) Get the aimed after installing, there are plenty of diagrams for you to use online but it's basically mark the center of the lights on a wall and put a piece of tape at centers, back up 25' and set the cutoff about 1 1/2"- 2" lower than the tape on the wall.
5) You probably don't need a relay harness as the stock bulbs draw more power than the HID's
6)LED's are just coming into fashion but
aftermarket LED's have not come close to achieving OEM stats and do not project light far enough. They look really bright in the front of the car while driving but objects and clarity in the distance fall way short of the lights you already have. They may be OK for fogs but there are lots of people on every auto forum who have tried these and removed them, especially high beams.
I have no vested interest in this company but here's where I would consider ordering HID's for you Coupe
http://www.diodedynamics.com/store/...dai-genesis-coupe-low-beam-hid-conversion-kit