I installed Spyder projector headlights with 55watt Xentec HID's with 6000k bulbs. The difference for me was astounding. As I've gotten older I have a crazy bad time driving at night. These really helped out. One thing to mention, as you go higher in temperature...above 6000k, the visible light is reduced significantly...so if you're running the 9000k or 10000k and expecting better visibility it's just not going to happen. I put 6000k in everything. I've installed Spyder projection headlights in all of my vehicles and several of my friends vehicles.
One thing about the HID ballasts...make sure you get the ballasts with the CANBUS defeat integrated in them. You can get around it but it's a super pain in the arse. You will need to run a couple of resistors for both low and high beam and on both left and right side (4 resisters total) and inline capacitors for your low beams. You'll also want to run a relay from your battery to power the ballasts. It's easy to do if you know electronics well (I have a degree in electronics so it's super easy for me).
If you get the headlights with the CCFL halo's I highly suggest you run a relay from your ignition to power the inverters for the CCFLs. Also be prepared to replace the inverters eventually...keep a couple on hand. They are cheap and when they fail it can be...violent. I had that happen last weekend on a friends truck. If one blows within a year, Spyder will send you a new one, no questions asked. Oh, they also suggest to wire the halo's to your parking lights so they only come on when your headlights or parking lights are on. Eff that.
Regarding the halo wiring, I opened my fuse panel, lifted it out of it's box, and spliced into a wire that went hot when the ignition turned on. I can't remember which fuse exactly but I've had 0 problems with my set up. The only problem now is they were installed on my Green Designo and as some of you know, I got drilled a couple of months ago so the car is out of commission. Mine were also not CCFL halo's as described above. Boy I wish they were though. CCFL's are awesome and super bright.
One thing mentioned is you will need to point the headlights after installation. Not a huge deal but you will need to do it. Just make sure you don't point them too high as you will piss off all oncoming traffic. Been there, done that.
Before you remove your old headlights, pull in front of your garage door, mark the beam focus on your garage with electrical tape, and when you install the new ones, point at the tape. That will get you pretty close to where you need to be.
Regarding the xentec ballasts...I'm a big fan. They are cheap and I've had 0 issues with them. I've installed probably 10 of them in various different cars and and trucks have never had an issue. I installed Opt7 ballasts into my friends truck this last weekend and couldn't tell a difference.
If you have any questions, shoot me a PM and I will see if I can help.